Figured I'd bump this because I now have a theory as to what stats each starter may specialize in.
In the livestream, the player's Popplio attacked after Hau's Litten and Pichu which likely suggests that Popplio will be the slow bulky starter of the group that also has emphasis on a solid Sp. Attack stat. If you look at previous trios the Grass-type mostly took the bulky route (as shown with every Grass starter except Treecko) and in the case of the ones aside from Snivy, were mainly slow as well. The only time the Water starter was the slow one with the bulky stats was Mudkip, back in 3rd Gen.
Litten having the most sleek design of the three suggests it'll be the speedy one of the Alola trio, and will probably also be a special attacker with weak defenses and HP. Going by the fact that three out of six previous gen starter trios had the Fire-type as the fast one, this would be likely. Also, it'll be the first time since 4th Gen that the Fire starter is the fastest of the trio, and while Fennekin had good speed it was still slower than Froakie who was 6th Gen's resident speedy starter.
And if that's to go by, Rowlet will likely be a physical attacker since its secondary type (Flying) mainly learns physical attacks, while its other stats will be mainly middle-of-the-road. I could see it still having good Speed, though it'll still be slower than Litten. If Rowlet goes down the middle-of-the-road route stats-wise it'll be a first for the Grass starter, since none of the previous Grass starters went down that path.
