In reply to FAF.

"Mariah voice is not THAT strong in her belts"
Oh. My. God. I can't even.
It's funny how a girl can just do some whistle notes and high (not necessarily good) belts can be compared to MC.
Yes, Ariana IS better than many many singers out there and has strong potential to go far in the music industry.
However she lacks the resonance in her belts and can't really enunciate while doing them. MC's belts are famous for their strong yet resonant quality.
Until now Ariana has proved that she can do some decent vocal runs. But again, decent and not quite comparable to many MC's extremely difficult vocal runs.
She also can't execute whistles as effortlessly as MC does (MC can hold a note, or do those legatos and staccatos in either airy breathy tone or a strong solid one while Ariana can just, you know, "hit" it)
I watched many studio + live videos of both artists to make these judgments because I know every singer has his/her bad day and I don't want to come across as a biased stan.
Well, Ariana is Ariana and this is not a Mariah-copying contest. I believe that she should, and she will, be big, as Ariana - not anyone else, with or without her flaws.
Oops, I've digressed a bit :P
Yeah, MC's belts are anything but weak.
P/s: English is not my native language so there might be typos or grammatical errors here and there