It depends on the woman and the particular dress or pair of pants. BTW, some categories separate from dresses to add are skirts and gowns. I like to see the same women in all four so that I can get a better idea of their attributes before ranking them on the 1-10 scale. After all, that's what this is about, right?
Pants, skirts, gowns can frame the "buttockal area", as Jay Leno would say, to advantage. Dresses, as long as they are not those atrocious long dresses, and short skirts, and sometimes gowns, can display the legs to advantage. Dresses, gowns, and tops for skirts can display, again thanks to Jay for the terminology, the "bosomal area" to advantage.
But the real answer, I think that men prefer them in bikinis, thongs, underwear, lingerie, or nothing. (Assuming they are on the high end of the 1-10 scale -- otherwise ponchos or mu-mus.)