Yes, for a start you will be missing your foreskin. Secondly, it apparently reduces stimulus because it becomes desensitised so there's that. There's also no going back, it's not a hair cut it ain't growing back.
Circumcision rocks! Yes it makes the penis a lot less sensitive. But you gain so much in staying power. Could make the difference between your girlfriend climaxing and not. Plus it looks a lot nicer and is cleaner. Now I have a circumcised boyfriend there's no way I'd go back.
I've looked into this topic before, and there are SO many people who did it in their mid 20s and proved this theory of having " less sensitive " penis wrong. All of the people who did it late in their lives claimed that it feels the exact same if not better because the head is always revealed when having intercourse.