Of course Sora is stronger. Main characters get special treatment like that, cause is their story and how they developed as they face their adversities time and time again.
Okay, so what if it's hard sometimes? Especially in proud mode? Gamers like it hard, they like it when it makes them frustrated. If Sora was so powerful that you flew pass the game in a manner of hours, where is the fun in that? There has to be a challenge, cause then the game will suck. There wouldn't be a point on playing it. But, yes, he is strong, which is why I love KH2.