First of all, it would not bother me at all to swing with a guy who's bigger than me. In fact, I'd love to see the look on my wife's face when he's all the way in.
Second, vaginal volume does make a difference. Although I think
bear_n_bunny could have put it more nicely, there are some women who just have more space to work in. My first girlfriend was one of these. When we had sex for the first and only time, I could have gone on indefinitely, because I just wasn't getting a lot of stimulation. Considering that it was my first time, it should have been over in a few minutes. With the reduced stimulation, I was able to go much longer. Nevertheless, this girl who, in her own words, had been with "lots of guys" was very pleased with my average
length & girth (measured A to B, not C to D).
Also in reference to
bear_n_bunny's post, is my own take on bleeding after sex. My wife and I worked opposite shifts for several years. We would have dry spells followed by passionate, Olympic-style sex. It wasn't unusual, after a bout of strenuous sex, for her to have some bleeding. Her gynocologist said it was nothing to worry about and that we should slow down and use more lubricant. She was on Depo-Provera at the time, which we believed reduced her own lubrication. Now that she's off the treatments, we have had no such problems. I have no problem believing any part of this story. In fact, if the woman was taking hormone treatments as a result of having a hysterectomy early in life, then reduced lubrication could have contributed to the bleeding.
For those that ask "why all the concern about size" I offer one explanation: for the same reason that women starve themselves to look like fashion models. Just as women have a falsly preconceived notion that all men want waifish women, men have a similarly preconceived notion that all women want a guy who is hung like a horse. The difference is that women can torture their bodies to conform to an unhealthy stereotype. All a guy can do, short of dangerous and often unsuccessful surgery, is to verbally and mentally obsess about the size of his penis. While women stress over the size of their hips, breasts or butts, we stress over the size of our cocks. It's that simple.
In most cases, the first time a young boy compares himself to other body types is in a locker room situation where the offending member is on display for comparison and contrast. Boys in a locker room don't tease boys about the size of their ears. They've seen ears all their life. What they haven't seen is each other's penises. All of a sudden "how fast can you run" or "how much weight can you lift" becomes "what a tiny pecker!". Locker room myths reinforce this stereotype as teenagers boast of things they've never done. Men in adult films and magazines have, until recently, always been of above average size. Since most of those films and magazines were created to please men, one can only assume that the majority of men also want to see guys with large penises. We are conditioned to correlate penis size with sexual prowess. Even today, most men in adult media tend toward the larger side of average. Add to this the sharp contrast among responses to the question "does size matter?", and the end result is inevitable: a gender totally obsessed with the size of our genitals.