Simplicity/healing. Having assisted in circs on kids 3-9 & done a thousand + newborns, i can surmise that what they feel is not the whole picture. The older kids were put to sleep for an half hour procedure & delt with stitches & wounds that were swolen & itched terribly & required 1-2wks recovery, the infants often slept thru the procedure under a local, had no stitches, minimal swelling & seemed recovered in days, .
Yes. At least they complain more, however, it is a much bigger deal as an adult.
Surgery can hurt. Circumcision has generated many fables as well as benefits. It can hurt. Pain is perceived differently as an infant. Local anesthetic can be very effective either way. It is easier and quicker on an infant. It does not: shorten penis, reduce sensation , or cause other problems typically.
Circumcision. The answer to this question is difficult to ascertain. A grown man is very well aware of the severity of pain. Since a newborn boy cannot answer an interview, it will be hard to tell how painful the circumcision is. Unfortunately, the nature of his cry will not tell you that. I can only surmise that the quality and severity of the pain will be similar.