Well, beauty is much more subjective than talent. I think both ladies are attractive in their own ways.
As to talent, I personally feel there is no contest. Mariah has vocal ability that is amazing! I'll go as far as to say that she has more voice than she needs for the type of music she performs!
In fact, that's a frustration for me when it comes to Mariah. I like her music and all, but there's really not a lot of substance to it. So she ends up doing all those vocal acrobatics in her songs. And, it's not so much the ultra-high whistle-register notes she sings (which
are very impressive

) but rather all those unnecessary melismatic flourishes that make the song seem overwrought. It's like she's trying too hard to make the song sound like it's saying something. But, again, that's just a matter of taste.
Character? Of course I can't comment as I know neither of them, but I wish they'D both dump the "diva" thing. It has become a bit silly for them and tiring for the rest of us.