Nicole has a more powerful and versatile voice, as well as a larger range. It takes a lot of dedication and ability to sing opera. I understand that some prefer Demi's tone/are put off by Nicole's–but ability wise, I think that Nicole is the clear winner.
Both ladies have talent on singing that no doubt. Talking about vocal training, I think every singer should routinely perform vocal training to develop his/her vocal ability. If no, he/she may get problems on his/her vocal. Also vocal range and vocal technique can be improved with this vocal training. And for the singer, more mature his/her age, his/her vocal can be more mature & he/she can control his/her vocal more well. The exercise continuously will also help to control breathing which certainly is needed for every singer. Especially for Demi, she is very young lady singer so she has million opportunities to develop her vocal capability. Okay, in this poll, I vote Demi because I love her vocal colour and characteristic. And I also love this performance by her:
Both are really good but Nicole is far better.
In this poll you shouldn't vote who you like best but who has got a better voice and actually Nicole can do things that not many other singers can do.
It's true that Demi is still 19, but the question is pretty much clear and right now Nicole is just ... wow.
I feel like some of you should listen to her unreleased material, she's not the bitch the press makes her look like and it's worth it