I thought that the notion was that the foreskin protects the non erect penis from rubbing against pants and the like whereas the circumscised penis is more exposed. Hence the circumscised penis is less sensitive to stimulation (because it habituates to rubbing against pants and the like).

I remember my sister asking about this when she gave birth to a son. The doctors asked her which she wanted him to be circumscised or not. She asked about the pros and cons (and stated that religious reasons were not a factor). They said that it was easier to keep a circumscised penis clean but that keeping an uncircumscised penis clean isn't really all that much trouble so long as you are taught. The main thing for her is that yeah the operation has gotta be painful and also occasionally accidents happen which can result in the penis being amputated. The doctors also said that more and more people wern't getting their kids circumscised so she didn't need to worry about other kids poking fun at him either way. She decided not to go with (what she felt to be) an unnecessary operation that was largely for religious reasons (that she didn't believe in).

But I guess that means times are changing...

I've never been with (or really seen) an uncircumscised guy. But I guess that there will be more in the younger generation...