IMO the shape of the stock and the quality of the recoil pad make a greater difference than the choice between most of the cartridges mentioned. I had a Rem 700 in 35 Whelen with a good pad that did not bother me at all. A Rem 14 in 32 Rem with a steel butt plate was not comfortable for me to shoot. He should find a rifle he likes, that fits him well, and get a good pad put on it.
