I'd say that Ariana has the bigger career; Demi never came close to a top 2 hit.
Better voice - depends on what you like. Ariana has amazing high notes and technique, Demi has a stronger voice more suited for belting. I'd give Ariana the upperhand though because she's more consistent.
Ariana has the brighter future as well. She found something that really works for her, while Demi is still trying to find her place in the music industry that's going to give her long term success.
Ariana. Demi's sold more albums but Ariana's already bested her with singles and Problem is bigger than any Demi song. Ariana clearly has the better voice and brighter future so no explanation needed for that.
Then wait till Ariana catches up? If we say Demi sold more records y'all pull this "Ariana released less albums!!!11" well then don't compare her until she releases the same amount of albums.
Don't compare an artist that has been out for 8 years to one that's been out for a year and half mainstream. Overall I would say Ariana has achieved much more success WW and in the US, I mean she has 4 songs that have outpeaked Demi's entire discography. She's just a bigger artist than Demi regardless of sales (which shouldn't even be compared to Demi's because like I said she's been out for years and she SHOULD have way more in terms of sales)
Bigger Career: Ariana
Better Voice; Ariana
Better Future: The one who actually has growth in success and impact each era, not the one who is flatline and Mediocre.. :>>
