My immediate preference is on the slimmer side but I have been very pleased and satisfied meeting some bigger girls too. No difference. What made things good for me was that we liked each other, had similar likes, I made her orgasm lots, she played with my cock whether to just play with it or to drain it.
Curvy. My first time was with a quite curvy, overweight woman and I've been an absolute worshipper of curvy women since then.