I have been told by women that an inch or even two of length (girth being equal) doesn't make that much difference sensation-wise, unless the longer penis is long enough to bottom out and stretch the vaginal vault, or rub the cervix. In that event, the longer cock may be better, or it may be worse. I've been told by a fair number of women that they don't care for that sensation at all. For some women with shallow vaginas, a length of 7" may prevent complete insertion, which might reduce pelvic contact and diminish the pleasurable sensations. I've also been told by some women that they really get off on the sensation of a guy's scrotum banging against their vulva and perineum when going at it face-to-face, or against their clit when doing it doggy style, and that won't happen if the guy is too long.
I think most women would notice a big difference between a girth of 4.5" and one of 5.5". In my experience, a girth of 5.5" is on the borderline of being to thick for a small percentage of women, but I rather expect most would prefer 5.5" to 4.5" if they had a choice.
An extra inch or two of length can open up the door to a few more positions in which close pelvic contact isn't possible. It reduces the lilkihood of the guy repeatedly slipping out, and allows for longer strokes, which some gals enjoy. On the other hand, at around 7 inches insertable length I have been told by a couple of women that I was too long for comfortable doggy style (a massive dissapointment) or missionary with her legs up on my shoulders.