The moral of the story is that FFVI is better than FFVII in every aspect, except, of course, graphics. Sorry, that's the way it is.

But other'n that. Celes and her inner struggle, including the suicide attempt, were much more dramatic than Aeris being shiskabobbed on a big dumb sword. With Aeris, it's just this ignorant, innocent little girl that has completely unrealistic dreams. With Celes, you have a soldier, bred to be a warrior, so different from everybody else, but who shows that she still has the emotions and feelings of normal people, and strives to join them -- not lead them, not do her own thing, but to be a part of something greater.