who fights better?

[Davey Gaga]

Riku is far too overpowered. All you have to do is attack with the same number card as the opponent, then you go in duel mode. Win it, then he does a highly damaging attack. Repeat.

Isn't that the battle sequence for Riku in Re: CoM?

Like most others, I've only played the GBA version. I voted for Riku. I'd rather not go into the story again, but we all seem to be in agreement that Riku was stronger, anyway. As for the battles themselves, it's Riku again, for two reasons:
1) Riku is clearly the more adept fight - he is more confident with a weapon than Sora, requiring only one hand for starters.
2) Statistically, you can increase Riku's strength throughout the game.

 

[Gabranth]

I'm not sure, but I've never played as Riku in the GBA version. (No point since I have the PS2 version).

There are other reasons as to why Riku is stronger. For one, he fights alone. This proves his strength and braveness. Secondly,he kills Lexaeus AND Zexion both first time. You may say that Sora beat Marluxia and Larxene,but if you remember, he had Donald and goofy with him.

 

[Moogles]

For one, he fights alone.

You know, I never once considered that. Very good point. I wanted to make a case for Sora, but there isn't much to work with.

Riku is physically superior, seems to be more naturally gifted, and--as mentioned above--he fights without the aid from others.