http://thecircumcisiondecision.com/20000-nerve-endings/

http://www.foregen.org/human_foreskin

Both have pros and cons. Also, circumcision is no longer medically recommanded (in canada anyways. They recently, stopped recommand them). Circumcision is purely a cosmetic surgery.

Circumcision pros:
-Easier to clean.
-Pleases a lot of women (for looks).

Cons:
-If done in newborns. Newborns are at a increase risk of infections.
-Infections.
-Infancy, increase risk of dying then adult from the procedure.
-Infancy. Increase risk of circumcision done wrong.
-Sexual active adult won't be able to have the full sensation and may lead to sexual frustration.

Circumcision does not prevent STIs. Simply lowered the risk in adult hood.

Foreskins pros:
-in infancy. Foreskin protects the head from feces and such.
-Sexual active people: full experience of sexual sensation.
-Pleasure women in intercourse as the foreskin acts as a natural lube.

Cons:
-More work to maintain hygiene.
-Risk of UTI
-Risk of tare during sexual intercourse.