This is tough. I had been fast forwarding through the past few weeks, but I actually made myself sit there and watch the entire show tonight so I could discuss, lol.
It almost goes back to the old "someone who is going to be good now" versus "0o0o0o0o0o0 potential!" debate. Bo is the better singer right now (despite the fact Carrie has a better vocal range) in that Bo has more exeprience, and is more consistent when hitting his notes. However, Carrie shows many flashes of being the shiznat down the line. She is good now, and the more she sings the better she will get with hitting a lot of the notes that she tries to hit now that don't sound all that great. Plus, if you think about a studio voice where they can clean up vocals, etc. Carrie would blow Bo away because she has the expanded vocal range, as to where Bo tends to sing in one tone (although I was impressed he hit the nice note in the last song).
The only thing that works against Carrie is she seems to have one of those voices people either love or hate. Whatever happens, the person who wins will be deserving, yet there will always be controversy. I suppose we'd rather it be this than Anthony versus Scott or something that would make everyone go 0_o!
... oh, and while my sneeking suspicion is that Bo may win, I think I will root for Carrie.