I say keep both! The X alloys kinda suit it because they're not huge and they're period Fiat, which is appropriate. So they're not OTT and if you're in a sporty mood, you can sport the alloys!
However if you need to use the roofrack, you can do a quick arseaboutface to avoid a style conflict
I've had a "sporting" Panda. Done subtly I thing they can look good. Just sticking bits on without thought is not good. Spend money on it to keep it standard but in mint condition is always going to be a winner.
Despite the alloys taking the lead in the poll I'm ditching them. I like it too much with the steelies and roofrack. Pandas definitely suit the basic look more. I'll hang on to the alloys though, might be nice during the summer.