I reckon Wish Latias will be very useful; another useful Wisher will be nice.
 
I was thinking about Specs Latios vs Specs Salamence, and this is what I came up with. 
 
Salamence
-Has Intimidate, helpful in reducing Physical threats and makes Salamence bulkier on the Defence side of things, considering his higher HP and equal Defence anyway.
-Only has three weaknesses. Three is a pretty average number but five is quite a large amount. Salamence is therefore easier to pair with other Pokemon who cover all his weaknesses.
-Has a Fire move! Latios has nothing but HP Fire for a Fire type move, which is problematic since Steels are so widely used now. Dragon/Water is only a little more resisted than Dragon/Fire of course, but Fire moves do more damage to the metagame as a whole.
 
Latios
-Better in the sense that it is faster, and has more Special Attack (359) than Salamence even with a neutral nature. Salamence has to max his SpA with Modest to get to 350. This means that a Timid nature could be used on Latios and it would still be more powerful than Mence, whilst having great Speed. However, it may not need the +Speed nature; it still gets ahead of many Pokemon otherwise and Modest provides larger SpA.
-More resistances. Latios' typing is both a curse and a blessing; it is weak to many common types including Ice, Dragon and Dark (Pursuit), but it resists Grass, Psychic, Electric, Water and Fire which are all popular types, not to mention an immunity to Ground thanks to Levitate. Higher SpD means that it can take more of those Special Fire onslaughts than Mence. Plus, he's neutral to Stealth Rock rather than weak to it.
-Latios has a useable second STAB. Salamence's second STAB is Flying which, barring Hidden Power, meant that Salamence didn't have any Special Flying moves. He got Air Slash in Platinum, but it doesn't add great coverage anyway being that Fire already covers Grass and Bug. Psychic isn't a fantastic STAB having only two type advantages, but Psychic type moves tend to be powerful with useful side effects. 
-Finally, Latios gets greater Special coverage than Mence, what with the aforementioned Psychic STAB as well as added moves like Ice Beam, Thunderbolt, Shadow Ball and Energy Ball. It's still a shame he doesn't get a Fire move, but he gets Surf. This means Latios' set can be taylored more than Salamence's depending on the team's needs.
 
I reckon that Draco Meteor/Surf will be a standard, but the other moveslots will be pretty open. Thunderbolt, Energy Ball, Ice Beam and Psychic all have good advantages, plus there's always Dragon Pulse. A real thorn in Latios' side might be that Pursuit weakness, though.