Well, i've only ever had sex with one girl. She was overweight, definitely not excessively fat. First glance of seeing her naked, i've seen slimmer girls with more attractive bodies but that's irrelevant at the moment. Her skin colour was very beautiful though. After getting more comfortable with her and not being nervous, the sex was amazing. She got wet very easy and her body felt really good and her vagina was tight and I can't remember one session I didn't enjoy. When I am sitting on a chair and she came on top of me and started to do her action, then is when you really appreciate the great effect of a bit of weight.
With slimmer girls though, you'd have a bit better access with her bending over, especially if you're a guy in my case with an average (6") dick. Nonetheless, there is a slim girl who I am good friends with, am really attracted to her and really would like someday to have a taste of her in the bedroom. Her body rocks! There are times were she leans on me, as we're quite close friends, and her body feels amazing, much better than the girl I mentioned above who i've had sex with.
In conclusion, there's advantages and disadvantages. Once you love the girl and cherish her, it wouldn't matter if she's fat, slim, average etc. The girl above, she hardly did anywork, and we had sessions of intercourse lasting 45 mins where it was excellent for both of us. She don't mind not doing anywork, and neither do I. But damn, I gotta say, its a good thing I played sports, it requires great deal of stamina to go for 45 of intercourse with only breaks being to change positions. Ofcourse, that's with a condom, without condom maybe 25 mins before cuming. With a condom, I did manage 1 hour+, but before the hour, I started to get soft due to fatigue setting in. I stopped for a half hour then continued from there, so that's why I said its important to have stamina. Once you don't cum as yet, and you're getting fatigue and a condom on, I start to get soft. Has happened a few times to me, but that's after going for about 45+ mins.