I'm like onesnowyowl....I tend to have big ones when I'm masturbating. When I am with a guy I tend to have lots and lots (and lots) of smaller ones. It's all good, either way!
I do find that if I am on top of the guy I tend to have stronger ones then in the old missionary position. My best, biggest, "rock my world" O's have come when he's doing me from behind and touching my clit at the same time. Then it's......OH BABY!