Ariana is more consistent, so I'll go with her. Demi is very hit and miss and Ariana has much better technique. Plus, I much prefer her tone but that's just opinion.
Not that familiar with them, but it seems like Ariana has a stronger voice overall, but her tone is too thin sounding. It's just a little too shrill imo.
Ariana has a remarkable voice for someone her age, but she's very overrated. Demi has a much stronger voice and I think she's an overall better singer.
Ariana and it's not even close. I never got the fuss about Demi's vocal ability and to make matters worse some of her performances are sloppy imo. Ariana can do no wrong