I feel a little more attached to Roxas than I do so Sora. He was more easy to relate to I guess. Sora really only had one emotion through most of the games: happy. If he felt anything other than that, he didn't show really show it.
Wow, it's been a while since I've seen one of these. The "better half" makes it sound like we should pick on who's the good one, though, in terms of who's the purest. Nonetheless, I prefer Roxas completely. Sora might have that hidden Darkness within that he keeps away with a smile, but he's still sort of bland to me. Roxas (other than Riku), was one of the characters who actually had very negative traits to them and earned some of the consequences that came about: temperamental, selfish, short-sighted, a bit of a jerkass, attitude problem, etc. I appreciate the hcraacter for that, since we've had too many cookie-cutter people. He has a lot of quirks, and he manages to balance it with a little cheerfulness, and concern for his friends. He isn't a stranger to laughter.
I like Roxas a bit better for the same reasones that most people already stated: he seems a more realistice and realatable than Sora. I thought Sora was cute in KH1 and CoM but then KH2 came around and it was like (diflate) phlumephlubephlubephlubephlube.
If you mean by 'better' as in combat style and in those things, I'd say Sora. Roxas doesn't even know that he can summon keyblade from a distance (see the cut scene of their battle), and seems that Sora has better control of keyblades.
If meant by more humane or as which one I like more, I'd say Roxas.