Status: Done
From the (Edit: previous) on-site analysis, Other Options.
"Shiftry can Swords Dance to boost its Attack stat, but this begs the question of 'what physical attacks it would use?'. In general, its special attacks are more powerful than whatever physical attacks it can muster. For what they are worth, Faint Attack, Razor Leaf, Rock Slide, X-Scissor, Aerial Ace, Payback, Return, Brick Break, Double-Edge, Explosion, and Quick Attack are the total of Shiftry's physical attacks. Fake Out is also on offer, but is only really viable in 2v2 matches."
I don't know when Shiftry's movepool expanded so much, but none of these attacking moves are contained in the set. Concerning Absol, Shiftry has several advantages to bring to the table:
STAB Seed Bomb
25 more Base HP (50 more HP)
Resistances to Water, Grass, Electric, Ground, and immunity to Leech Seed
Potential Sunny Day speed boost (though it's not necessary thanks to Sucker Punch)
Ability to fake a Special set
Still, Absol will certainly get a mention in the comments, as 30 higher base attack is something one must justify not using before choosing Shiftry.
[SET]
name: Swords Dance
move 1: Swords Dance
move 2: Sucker Punch
move 3: Seed Bomb
move 4: Low Kick
item: Life Orb
nature: Adamant
evs: 4 HP / 252 Atk / 252 Spe
[SET COMMENTS]
<p>This set makes use of Shiftry's higher Attack stat, which it can quickly boost with Swords Dance. Shiftry has six resistances and one immunity, so finding an opportunity to come in and set up a Swords Dance should not be too difficult. Using this set will require a decent amount of prediction, however, as Sucker Punch will only work when the opponent is using an attacking move. When opponents try to get around Sucker Punch by using non-damaging moves, you should respond either by using one of your other attacking options or by further boosting your Attack with Swords Dance.</p>
<p>Shiftry has a rare and powerful tool in its STAB Sucker Punch. Combined with STAB Seed Bomb to hit bulky Water- and Ground-types and Low Kick to hit Steel-types, Shiftry has the ability to hurt both walls and sweepers alike. Still, Shiftry's coverage is somewhat limited by the fact that both Sucker Punch and Low Kick have limitations that prevent them from working effectively in certain situations. Sucker Punch can be unreliable for reasons already mentioned, while Low Kick doesn't hit Clefable or Chansey any harder than Seed Bomb does (due to their low weight). Thanks to Sucker Punch, Shiftry can afford to run an Adamant nature, which allows it to pack quite a punch after a Swords Dance.</p>
<p>While not neccessary, sun support will greatly aid this Shiftry, allowing it to reach 518 Speed, outspeeding pretty much anything in the metagame. Only faster Chlorophyll users and Choice Scarf users with base 110 Speed and a positive nature or base 125 Speed and a neutral nature will outspeed Shiftry in the sun. Of these Pokemon, the most common is Jumpluff, who can outspeed Shiftry and hit with a 4x effective U-turn, or Encore Shiftry's Swords Dance. Sun support allows Shiftry to strike first with any of its moves, as opposed to just Sucker Punch. This reduces your reliance on Sucker Punch, so Shiftry can sweep much more reliably against an opponent who is trying to out-predict you with moves like Substitute or Will-O-Wisp. Sunshine will also hurt Toxicroak, who resists every move on this set due to its Dry Skin ability.
[ADDITIONAL COMMENTS]
<p>This set runs into problems against Pokemon who can outspeed it and set up Substitute or use status moves to circumvent Sucker Punch. Such Pokemon include Mismagius, Alakazam, Espeon, and Sceptile. Shiftry can still come out on top against these Pokemon, but it must predict their moves extremely well by using Seed Bomb as they use Substitute and using Sucker Punch when they decide to attack. Note that with Sunny Day support, this becomes a non-issue. Toxicroak resists every move on the set, and can hit Shiftry super effectively with either of its STAB moves. Hitmontop resists Sucker Punch and can hit Shiftry with priority of its own. However, these Fighting-types can be finished off if they've been somewhat weakened, as a +2 Sucker Punch hits decently hard even when resisted. Pokemon who resist Seed Bomb and Low Kick but not Sucker Punch can still cause this set problems if they avoid attacking Shiftry at predictable moments. These Pokemon include Moltres, Altaria, and Venasaur. It may be tempting to run Aerial Ace or Rock Slide to deal with these Fighting-, Flying-, and Poison-types, but it is not recommended considering that most of them either outspeed or hit Shiftry with priority. Arcanine may seem extremely troublesome to Shiftry, but offensive versions can be KOed by a +1 Sucker Punch after Stealth Rock (or a +1 Low Kick, if you think it will use ExtremeSpeed).</p>
<p>Defensively, Shiftry enjoys having a bulky Water-type on its team. Slowbro is a good choice, as it can take on the Fighting-types who give Shiftry trouble, in addition to Fire-types and physical users of Flying-type attacks. Shiftry also requires offensive support, as it is unlikely to sweep a majority of teams on its own. Toxicroak is an interesting option since it functions very similarly to Shiftry, and together the two can power through their counters. However, such a strategy is risky, as some counters (such as SubRoost Moltres) are very capable of taking on both in the same match. As such, you may want to pair Shiftry with one or more sweepers who offer contrasting coverage, such as Moltres, Alakazam, or Mismagius. When using this strategy, it is also recommended to have a wall-breaker, such as Blaziken or Nidoking, who can pose an immediate threat to your opponent's team. Every Pokemon your wall-breaker removes is a potential counter to one of your sweepers, allowing you to eventually find an opportunity for a clean sweep. Shiftry's sweeping partner should preferably be able to deal with Weezing, who walls Shiftry easily. Shiftry will also enjoy having a teammate who sets up Stealth Rock, as it will aid Shiftry greatly against the Flying-types who resist its Grass- and Fighting-type attacks.</p>
<p>When considering Swords Dance Shiftry, one should evaluate the merits of using it over Absol, who sports a much higher Attack stat, in addition to the powerful Superpower for coverage. In general, Shiftry's advantages over Absol stem from its Grass typing. STAB Seed Bomb is an excellent weapon for taking out UU's physical walls, and its three most useful resistances (Water, Electric, Ground) are provided by the Grass type. In addition, Shiftry has a much higher HP stat than Absol, giving it the chance to make use of its resistances. Finally, Shiftry is most commonly seen running special attacks, so your opponent might not make the best move when he or she first encounters Swords Dance Shiftry. The choice between the two is largely up to the style of play that you want to use with your Sucker Punch sweeper. If you prefer Absol's power and don't mind its frailty, it is the better choice. However, if you feel that extra bulk and resistances will help you set up more consistently, or find that Absol runs into problems against bulky Water- or Ground-types, then Shiftry is the best option.

From the (Edit: previous) on-site analysis, Other Options.
"Shiftry can Swords Dance to boost its Attack stat, but this begs the question of 'what physical attacks it would use?'. In general, its special attacks are more powerful than whatever physical attacks it can muster. For what they are worth, Faint Attack, Razor Leaf, Rock Slide, X-Scissor, Aerial Ace, Payback, Return, Brick Break, Double-Edge, Explosion, and Quick Attack are the total of Shiftry's physical attacks. Fake Out is also on offer, but is only really viable in 2v2 matches."
I don't know when Shiftry's movepool expanded so much, but none of these attacking moves are contained in the set. Concerning Absol, Shiftry has several advantages to bring to the table:
STAB Seed Bomb
25 more Base HP (50 more HP)
Resistances to Water, Grass, Electric, Ground, and immunity to Leech Seed
Potential Sunny Day speed boost (though it's not necessary thanks to Sucker Punch)
Ability to fake a Special set
Still, Absol will certainly get a mention in the comments, as 30 higher base attack is something one must justify not using before choosing Shiftry.
[SET]
name: Swords Dance
move 1: Swords Dance
move 2: Sucker Punch
move 3: Seed Bomb
move 4: Low Kick
item: Life Orb
nature: Adamant
evs: 4 HP / 252 Atk / 252 Spe
[SET COMMENTS]
<p>This set makes use of Shiftry's higher Attack stat, which it can quickly boost with Swords Dance. Shiftry has six resistances and one immunity, so finding an opportunity to come in and set up a Swords Dance should not be too difficult. Using this set will require a decent amount of prediction, however, as Sucker Punch will only work when the opponent is using an attacking move. When opponents try to get around Sucker Punch by using non-damaging moves, you should respond either by using one of your other attacking options or by further boosting your Attack with Swords Dance.</p>
<p>Shiftry has a rare and powerful tool in its STAB Sucker Punch. Combined with STAB Seed Bomb to hit bulky Water- and Ground-types and Low Kick to hit Steel-types, Shiftry has the ability to hurt both walls and sweepers alike. Still, Shiftry's coverage is somewhat limited by the fact that both Sucker Punch and Low Kick have limitations that prevent them from working effectively in certain situations. Sucker Punch can be unreliable for reasons already mentioned, while Low Kick doesn't hit Clefable or Chansey any harder than Seed Bomb does (due to their low weight). Thanks to Sucker Punch, Shiftry can afford to run an Adamant nature, which allows it to pack quite a punch after a Swords Dance.</p>
<p>While not neccessary, sun support will greatly aid this Shiftry, allowing it to reach 518 Speed, outspeeding pretty much anything in the metagame. Only faster Chlorophyll users and Choice Scarf users with base 110 Speed and a positive nature or base 125 Speed and a neutral nature will outspeed Shiftry in the sun. Of these Pokemon, the most common is Jumpluff, who can outspeed Shiftry and hit with a 4x effective U-turn, or Encore Shiftry's Swords Dance. Sun support allows Shiftry to strike first with any of its moves, as opposed to just Sucker Punch. This reduces your reliance on Sucker Punch, so Shiftry can sweep much more reliably against an opponent who is trying to out-predict you with moves like Substitute or Will-O-Wisp. Sunshine will also hurt Toxicroak, who resists every move on this set due to its Dry Skin ability.
[ADDITIONAL COMMENTS]
<p>This set runs into problems against Pokemon who can outspeed it and set up Substitute or use status moves to circumvent Sucker Punch. Such Pokemon include Mismagius, Alakazam, Espeon, and Sceptile. Shiftry can still come out on top against these Pokemon, but it must predict their moves extremely well by using Seed Bomb as they use Substitute and using Sucker Punch when they decide to attack. Note that with Sunny Day support, this becomes a non-issue. Toxicroak resists every move on the set, and can hit Shiftry super effectively with either of its STAB moves. Hitmontop resists Sucker Punch and can hit Shiftry with priority of its own. However, these Fighting-types can be finished off if they've been somewhat weakened, as a +2 Sucker Punch hits decently hard even when resisted. Pokemon who resist Seed Bomb and Low Kick but not Sucker Punch can still cause this set problems if they avoid attacking Shiftry at predictable moments. These Pokemon include Moltres, Altaria, and Venasaur. It may be tempting to run Aerial Ace or Rock Slide to deal with these Fighting-, Flying-, and Poison-types, but it is not recommended considering that most of them either outspeed or hit Shiftry with priority. Arcanine may seem extremely troublesome to Shiftry, but offensive versions can be KOed by a +1 Sucker Punch after Stealth Rock (or a +1 Low Kick, if you think it will use ExtremeSpeed).</p>
<p>Defensively, Shiftry enjoys having a bulky Water-type on its team. Slowbro is a good choice, as it can take on the Fighting-types who give Shiftry trouble, in addition to Fire-types and physical users of Flying-type attacks. Shiftry also requires offensive support, as it is unlikely to sweep a majority of teams on its own. Toxicroak is an interesting option since it functions very similarly to Shiftry, and together the two can power through their counters. However, such a strategy is risky, as some counters (such as SubRoost Moltres) are very capable of taking on both in the same match. As such, you may want to pair Shiftry with one or more sweepers who offer contrasting coverage, such as Moltres, Alakazam, or Mismagius. When using this strategy, it is also recommended to have a wall-breaker, such as Blaziken or Nidoking, who can pose an immediate threat to your opponent's team. Every Pokemon your wall-breaker removes is a potential counter to one of your sweepers, allowing you to eventually find an opportunity for a clean sweep. Shiftry's sweeping partner should preferably be able to deal with Weezing, who walls Shiftry easily. Shiftry will also enjoy having a teammate who sets up Stealth Rock, as it will aid Shiftry greatly against the Flying-types who resist its Grass- and Fighting-type attacks.</p>
<p>When considering Swords Dance Shiftry, one should evaluate the merits of using it over Absol, who sports a much higher Attack stat, in addition to the powerful Superpower for coverage. In general, Shiftry's advantages over Absol stem from its Grass typing. STAB Seed Bomb is an excellent weapon for taking out UU's physical walls, and its three most useful resistances (Water, Electric, Ground) are provided by the Grass type. In addition, Shiftry has a much higher HP stat than Absol, giving it the chance to make use of its resistances. Finally, Shiftry is most commonly seen running special attacks, so your opponent might not make the best move when he or she first encounters Swords Dance Shiftry. The choice between the two is largely up to the style of play that you want to use with your Sucker Punch sweeper. If you prefer Absol's power and don't mind its frailty, it is the better choice. However, if you feel that extra bulk and resistances will help you set up more consistently, or find that Absol runs into problems against bulky Water- or Ground-types, then Shiftry is the best option.