Diana has a more sophisticated voice and I can see it being developed into a career that can handle a variety of styles.
Fantasia is a great performer and has a knack for drawing in the viewer. I think, though, that her voice may not be as rich.
If I close my eyes and listen, Diana is the better singer and Fantasia, the more seasoned entertainer. So I guess it is a matter of how weighty each factor is.
I do believe that I would tire of Fantasia's voice long before I would Diana's.
I forgot to add that my #1 pick would have been LaToya. She had it all; beautiful voice, stage presence and looks. I lost a little bit of heart when she was rejected.