The 3 Amigas...that made me laugh, lol, and yeah, it made me come check out the thread. It worked! But I read it as Three Amigos and wondered if someone really was wanting to discuss the 80's movie with Steve Martin, Chevy Chase, and Martin Short.
"The Best" in what way? If you mean vocally I suppose it would be considered Ariana Grande. Didn't even Quincy Jones comment that she was strong vocally, and he has worked with some of the best. But best could also mean as a stage presence, do you mean that...or song writer? I'm not sure if Selena could be viewed as being the best vocally out of these three, or even the best song writer, and yet, when she performed that song live at the AMAs that she had written "The Heart wants What it Wants" it was a powerful performance....a performance that could be "felt".
So, what are you picking; what do you mean by "best" when you say... best?