Right now I can tell you this: Despite having only a double jump (instead of the typical 2.5 jumps most characters have [the .5 is the up b]), Yoshi is HARD to gimp. Even against CPUs (and the Cpus are STUPID), I can't Gimp a Yoshi.
To Yoshi mainers, please tell me how you're supposed to play Yoshi. It'll help my judgment, and not look like a fool, again.
To help the Yoshi mainers with their own verdict, Here is a crash course on PT:
Squirtle: Often called the ninja turtle, Squirtle is meant to fly around the stage and hit opponents from the air (along with the occasional throw). However, After months of the developing metagame, Squirtle, while easy to learn, is the least reliable of the three, especially when fatigued. He lacks a KO move (barring usmash and dthrow, which typically work at over 100%), a lack of a meteor (making gimping that much harder), and several other problems (no projectile, light, slow ground speed), this should be the easier match.
Ivysaur: While Squirtle is meant to run around and try to fly, Ivysaur is meant to sit still, spam the long ranged move, and wait for the opponent to make the stupid mistake to run into Bullet seed and Usmash. Ivysaur's air game isn't bad either, Bair has great range, and Uair and Dair are two of his (I consider Ivysaur a he) KO moves (the third is Usmash). If you see a good Ivysaur, that means the player really took the time to learn him, as he is the hardest to learn with a primarily defensive play style (and a sucky recovery). Tread with some caution here, but Ivysaur is typically easier than...
Charizard: Yes, the orange mini dragon is considered by most professional PT's (all 8 of us, or at least all 8 that actually know of this site) as the most practical Pokemon PT has (and if you play the games, this actually makes sense, as Charizard is the most powerful). Charizard has several strategies under his sleeve (if he had any), including grab game, gimp game, pummel game, and more. Chairzard has Flamethrower (racks up damage), Rock Smash (alternate to both flamethrower and fsmash, depending on conditions), and Fly (I have found ways to KO someone with this move). He has decent vertical recovery (two air jumps and fly, his up B) along with the ability to glide (Horizontal recoveries are nearly infinite). Charizard is the one holding the team together, so he is likely the one to beat you (or at least be even with you). He is large though, but that is about the most obvious weakness he has.