I am 7" and what I feel is what I have always felt, and I don't know if it feels more intense than what you feel or not. There are very, very, very few men who are 9" or thereabouts.
I know a couple of things about length, though. In slow sex whan you are using all your length, extra length makes each thrust more pleasurable for women, and probably for us men. In shallower positions, men who are longer can get better penetration. I cannot ever recall slipping out of any position, it may have happened sometime in the distant past, but I cannot recall.
Really, really long has some problems. Much longer than mine and you risk hurting your partner. Most vaginas can fit most penises with enough arousal, but it takes a long time to get to that arousal. I know I can hurt women with my 7" if I'm not careful.
My personal size preference comes from my girth at 6", which looks good and which women do enjoy.