great question...
difficult to answer.
Great clothes make other women want to be us. Also, there is the possibility it will lead to sex, great or not.
Great sex is an experience, intimate and oddly communal. No one will know we had great sex except for ourselves and our partner. Unless one likes to share, but that is a whole different topic.
Great clothes last decades longer than great sex. BUT, if you keep the same partner, great sex eventually becomes amazing sex - intimate and compelling, but without the frantic fear which defines truly great.
I can rock bad clothes. I remember wearing something when I was about 14 that my Grandmother (not the chic french grandmother) had made for me - imagine a laura ashley sofa, wrapped knee to neck around a geek, with a six in belgian lace collar. One of the more catty seniors in HS attempted to tease me about it - I just looked at her and told her she was jealous. She had no retort.
I actually wear the blouse with crisp white pants - it looks suprisingly good with the right accents.
I think I'd prefer great sex, as long as it came with a guarentee that the sex will be consistant, and never dip below the level of good. Or, if I could change my mind at any time after.