there's definitely room for both in my world and I like Diet Coke fwiw. I just think Coke Zero is far and away the better soda and will probably die out, whereas Diet Coke will keep selling in copious quantities and no one will much care that Coke Zero vanished overnight. but I'm saying it before it happens: I'm gonna miss Coke Zero. I really am
I like the fact you can try whatever the hell concoction you can come up with though. I hardly see them much anymore though