I thought it was a nice ass and abs that the ladies were hot for. In truth, it is probably the whole package and not just body parts that turn women on.
NO STOP, YOU WERE RIGHT THE FIRST TIME! We like booties and wheels. Abs are good too, but abs minus wheels equals NO FUCKING DICE.
Anyway, I have basically no arms at all, but my biceps only make a difference if I'm flexing AND really really lean. My triceps, on the other hand, show when I'm wicked soft and pretty much doing nothing. So I'm going all in for triceps, with the obvious caveat being that I have huge legs and a decent dumper, so my arms don't matter at all anyway unless I'm wearing some kind of retarded sweatpants.