People say they prefer the taste. I don't know that I could tell the difference though.
This usually pops up around Passover, when Coke switches to an all sugar formulation for reasons I'm unqualified to explain. It's an "oh hey, this Coke tastes different", I'll check the label, and see that it's sweetened with sucrose instead of HFCS.
I'll handwavingly claim that this is close enough to a blind study/anecdote as I'm not Jewish and haven't a clue when Passover falls. As I buy cans, not bottles, it's not the yellow caps giving it away either.
Pepsi tastes much sweeter than Coke and I wouldn't be surprised if corn syrup Coke was sweeter than sugar Coke.