There is no difference in circumcised and uncircumcised. You're not more likely to get an STD, it feels the same, it only looks different. I, myself, am uncircumcised, because NOBODY comes near my penis and cuts ANYTHING off.
Really, the only reason people still do it, is because it's biblical. Then again, I've seen non-Jews with that were circumcised. So I guess I don't really know why most people do it. They just do.