I find the whole thing to be so weird. Curls are inherently seen as playful, flirty, and youthful. Shouldn't those be qualities men find ATTRACTIVE? I don't get it.
Guys seem to love playing with my curls. One special someone hates it when I get a blow-out (and I only do it about 2-3 times a year). Even though I think my straightened hair looks great on me, he insists I look the best with my naturally curly hair.
I will say that men seem to undoubtedly favor LONG hair above anything else...no matter the texture. Since most curlies have hair that doesn't show its true length potential (hello shrinkage?), that may be a factor. The compliment I hear most often when I straighten my hair is, "Ooh! It looks SO loooong!"
I think long hair is more equated with femininity and sensuality than straight hair.