I don't understand why they didn't give Empoleon a typing that could defeat the other two starters. I mean Infernape can use Stab fire moves on Torterra and Stab Ground on Empoleon, Torterra can use Stab Ground moves to destroy Empoleon and Infernape. However, Empoleon can only use Stab super effective water on Infernape. It's water moves are neutral against Torterra which I guess is better than being resisted. It cant use it's Stab steel type moves super effectively against the other types. But I guess that's why Ice Beam is always a viable option to nuke Torterra and Cynthia's Garchomp. Also it's weird that Empoleon cant learn a water recoil damage move. I mean Infernape gets Flare Blitz and Woodhammer for Torterra. And Empoleon cant resist fire type moves as they are neutralized by it's steel typing. Water/Steel is a decent typing but there are so may better steel types like Lucario, Magnezone, Steelix, Bronzong. Plus there are so many better water types as it is the most dominant type in the game.
Anyways, I think Turtwig is my favourite. I love Torterra's move pool and I found it extremely useful during game play. I would never use it in competitive play as it is so slow.
Infernape is probably the best for playing the game as there are limited fire types obtainable in Sinnoh. Thank you Game Freak for giving us three consecutive Fire/Fighting types in a row. It's a good typing but no need for three in a row.