Not quite, as I explained at the beginning of this threat why they are so different. I am not going to repeat the entire point I made there. They aren't the same, but yet they are always competing for a teamslot. Obviously, there are differences, and as such, sometimes the choice is very clear (if you need that Ground-coverage, you will use Sawsbuck, if you need a Grass-type that can deal a lot of damage to Psychic-types, Leavanny is your choice, and if you need Baton Pass capabilities, Leafeon is often the best option (still competes with Leavanny if you need a Fighting-resist)
While Nature Power is very significant and Sawsbuck has a very powerful Double Edge, it cannot OHKO Golurk with significant HP investment (248 HP and 8 Def prevent the OHKO even regardless) or 2HKO Alomomola with Horn Leech, which plain sucks. It requires Adamant to achieve these KO's... and suddenly it is slower than Leavanny or Leafeon who can go with Jolly to achieve these KO's.
Yes, its Double-Edge is very powerful, but we all know how quickly Double-Edge and Life Orb rack up damage, cutting badly in Sawsbuck's lifespan, and if we don't run Life Orb on Sawsbuck, well... then Leavanny hits harder, even when factoring in X-Scissor versus Double-Edge..
It also has many of the similar flaws as the other two, like being OHKO'd by Jynx, being frail as heck, outsped by Scolipede and Swellow, relatively bad typing, but also unique flaws (being Mach Punch weak, which I consider just as bad as Leavanny's SR weakness or Leafeon's lack of coverage).
Why I didn't complain about Giga Drain is simple - you don't miss out on annoying OHKO's and 2HKO's as far as I know, some have Leaf Storm to use alongside when they desire the raw power (like Exeggutor) and SolarBeam exists in the sun, and those who haven't can boost up quick and have the bulk to do so.
Victreebell is top-C and requires Sun to function. Leavanny, while being capable of functioning without it, functions way better under the Sun too, as it is capable of outspeeding every Scarfer under the Sun (same goes for Sawsbuck and Leafeon though). That being said, they can all afford to run Adamant under the Sun, but if you can't get Sun up for some reason you're screwed).
Also, Leavanny isn't that frail. It can take most neutral attacks and some SE attacks as well (like Leafeon's X-Scissor), since its bulk is actually similar to Leafeon's, though more rounded. Leavanny also deters CB Sawk from using Earthquake on your Misdreavus switch-in (which is very significant actually if you happen to run both since Stone Edge and Ice Punch suck if you are locked into them), can take Sawk's CB Close Combat after Rocks as well and turns a variety of mons in complete liabilities if someone happens to run them.
I did not know Sawsbuck had Faint Attack access, though - but Faint Attack requires it to give up Nature Power, a STAB move or Swords Dance, and you just said how significant Nature Power is (and I think we agree STAB on Double-Edge and Return are reasons to use Sawsbuck over its fellow Grass-types as well, leaving replacing Horn Leech as the only option but then why aren't you using Kanga?). Also a neutral Double-Edge hits harder than a Super-Effective Faint Attack. Leavanny however, has only three significant moves: Leaf Blade, X-Scissor, and Synthesis or Swords Dance, leaving your fourth moveslot to be whatever you desire in that slot, like Heal Bell, Substitute, Baton Pass, Shadow Claw, Knock Off, Light Screen, Reflect, Agility, Return or even Leaf Storm (for things like Regirock, defensive Carracosta and Gurdurr after a Bulk Up).
