which looks better on your transcript: sports or clubs?

Neither sports nor clubs go into a transcript. A transcript is a record of classes taken, grades received, academic honors bestowed and degrees conferred.

I would say clubs because you can be in any club: chess, literary magazine, science, drama, whatever. But find a couple of clubs that you love and stick with them. If you jump around every year changing what club you are in, it doesn’t impress admissions.