Catching up to the crowd again! Or cheating...not quite sure which :P
Masuda Yuka and Takahashi Ai (tie)
I can love idols who don't have amazing voices, but when it comes to choosing my favorites based on voice alone, I am extraordinarily picky. Probably too picky. If I were a music teacher, my students would hate me for being a perfectionist asshole (partly why I stopped being a music major a long time ago).
But here in the privacy of my own home, I can be an asshole without hurting anyone's feelings. In my underwear, even.
I've never had anything nasty to say about either of these lovely ladies. Ai is by far the most talented singer Hello! Project has ever had. She has a huge range, a gorgeous vibrato and surprisingly good technique, which is rare for pop singers of any kind unless they've had some serious coaching.
Yuka has a gorgeous tone, and is fantastic both live and in studio. Since I'm just starting to become a slightly-more-than-casual AKB fan, that's really all I can say about her, but I love what I've heard so far.