Coke Zero is my preference, but I'll still take Diet Coke over regular. It's less to do with taste though, since all 3 taste like 99% identical. I just think the amount of sugar in regular Coke is obscene and disgusting.
Somebody tried to tell me that they all tasted the same. I called BS, that I could easily tell the difference. He had me do a blind taste test. I was right, I could easily tell which was which by taste.