I'll admit I don't like copy-cat characters...pretty much, in a game, movie, anime, etc., when one or more character is the EXACT same as another character, in either appearance, personality, or both.
I do not like Aqua because I feel she is too flat and plain. Plus I think she's overrated in terms of attractiveness. I'd pick Xion over Aqua ANY day
I'm alright with Terra, if it weren't for his appearance I don't think I would've liked him AS much.
And I have a soft spot for both Roxas and Sora, so I am just obligated to like Ventus.
The story for BBS, overall, I loooooved. It was saddening, and Master Xehanort was (and is) a crazily, amazingly, well-designed bad guy from which the likes I have never seen.
I'll take Sora, Riku, and Kairi, and Roxas, Axel, and Xion, over them any day, but I still really like the game. I love the idea of the split character thing! It's similar to Crisis Core in that aspect.
I've never played BBS, only watched the cutscenes and read about it. I don't have a PSP but my friend said she'll let me borrow hers