From NORM: (edited for brevity)
The Lost List
Many people think circumcision removes nothing more than a little extra skin. The truth is that circumcision removes several critical components of male sexual anatomy. This list enumerates everything currently known to be lost when one is circumcised. Included are notes on whether these losses can or cannot be amended by foreskin restoration.
It should be pointed out that circumcisions performed in North America may be more severe than those done elsewhere. In the United States, most hospital circumcisions are done to the Bris Periah standard of removing every ounce of foreskin and, in a large percentage of cases, some shaft skin.
Foreskin
The foreskin comprises roughly 50% (and sometimes more) of the mobile skin system of the penis. If unfolded and spread out flat, the average adult foreskin would measure about 15 square inches - the size of a three-by-five index card. This highly specialized tissue normally covers the glans and protects it from abrasion, drying, callusing (also called keratinization), and contaminants of all kinds.
Restorable
Frenar band
The frenar band is a group of soft ridges near the junction of the inner and outer foreskin. This region is the primary erogenous zone of the intact male body. Loss of this delicate belt of densely innervated, sexually responsive tissue reduces the fullness and intensity of sexual response.
LOST There is no known method of restoring the frenar band.
Gliding Action
The foreskin's gliding action is a hallmark feature of the normal, natural, intact penis. This non-abrasive gliding of the penis in and out of its own shaft skin facilitates smooth, comfortable, pleasurable intercourse for both partners. Without this gliding action, the corona of the circumcised penis can function as a one-way valve, making artificial lubricants necessary for comfortable intercourse.
Restorable
Meissner's Corpuscles
Circumcision removes the most important sensory component of the foreskin - thousands of coiled fine-touch receptors called Meissner's corpuscles. Also lost are branches of the dorsal nerve, and between 10,000 and 20,000 specialized erotogenic nerve endings of several types. Together these detect subtle changes in motion and temperature, as well as fine gradations in texture.
LOST There is no known method of restoring Meissner's corpuscles or other specialized sensory nerve cells. However, restoring and restored men almost universally experience tremendous increases in sensitivity, in part because the highly sensitive nerve cells in the glans are no longer buried under several layers of keratinized skin.
Frenulum
The frenulum is a highly erogenous V-shaped structure on the underside of the glans that tethers the foreskin. During circumcision it is frequently either amputated with the foreskin or severed, which destroys or diminishes its sexual and physiological functions.
LOST If the frenulum is amputated, there is no known method of replacing it. If only a small portion of the frenulum is left, it is probably no longer functional as a tethering structure. There is no known method of attaching it to a restored foreskin, but some men have reported stretching the frenulum remnant as they stretched their foreskin.
Oh there are too many more but they include immunological cells that help protect against infection, cells that produce pheromones - you can read the whole list on this link if you are interested.
Just to say, my DH is also circumcised - and he has definite loss of sensation in comparison to previous lovers who were not circumcised. I don't consider it a benefit.