And in comes the morning tilt..........sans-soda takes the lead!!
Aside from the fact that sugar in excess is bad, I wonder why we instinctively associate either one with something "bad"??
If we're talking about artificial sweeteners, I believe most sweeteners have been taken off the "carcinogen" list. You'd have to ingest the equivalent of a tanker truck full of the stuff to make it a carcinogen at which point almost anything is a carcinogen.
Add to that the debate that nobody seems to be able to decide whether coffee is good/bad for you. (I think the last study is still that it's 'good' in small amounts).
Maybe neither (again, assuming diet soda) are actually bad for you in the first place??? (shrug)