I absolutely love big girls. I've had skinny, curvy and fat girlfriends. And it can be said that sex is better with bigger girls. When I was younger I already had a preference for curvy girls. Big hips, thighs and huge boobs. I had some skinny girlfriends but didn't consider them very exciting. Besides that, it appears that bigger girls can better accomodate my cock. On the other hand, since my penis is quite a fatty himself it was cool to see that before penetrating a skinny girl, my cock looked extremely thick compared to their bodies.
However, my current girlfriend is a bbw. We met about 6 years ago when she was 105 kg (or 230 lbs) Right now she is about 145 kg (320 lbs) and 5.8" tall, so she gained quite a lot. But I love it. Her ass is huge, her G-cup boobies are to die for and her belly is so freaking soft. But above all, she is confident about her size, she is fit and loves being a bbw, which I think is a must. And her words are the following: Hey, a fat girl needs a fat cock. And I can tell you that doggy style is getting more and more awesome the fatter her ass gets.
Though, I do not know about "fat sex" with an ever bigger girl. She is only 26 years old and at this weight she starts to face the first problems like taking stairs and all that. I don't think I can be sexual attracted to a girl that is unhealthy, immobile, lazy or totally out of shape. I didn't discuss this with her but I think she shouldn't go beyond 160 kg (350 lbs). Either way, any other girlfriend I may have will be a bbw. I am too addicted right now.