"Slim" guys, I tend to feel less feminine and more domineering. I think it's my brain telling me "this guy is small enough for you to throw around, show him who's boss."
"Muscular" guys, my preference! I feel so good when I'm with my thick, strong, masculine man. I like to feel cute and sexy more than I like to dominate (although as some may remember, there are rare times I wish I could toss my man around like he does to me :tongue
and the feeling of his thick, hard muscles is just such a turn on. I love that he can just Fuck me any way he wants without any struggle and without getting winded. I also like being smaller than him, makes me feel more feminine.
"Fat" guys, I've had sex with my share of fat men.. Every over-weight guy I've been with, I had to do ALL the work... I was the only one to take my clothes off. I still had fun.. but it seems there's not as many possibilities physically as far as positions.. and it's always difficult to get into sex when one or both parties is self-conscious about something.
All this being said, none of it matters when you truly love someone. If my guy suddenly lost/gained 50 lbs of muscle/fat.. I'd love him just as much and I'd fuck him just as often... as long as HE was still HIM.