I shoot inexpensive 110 and 158 grain .357 magnum in a GP-100 5" at the range and, to me, they do not kick "that" much harder than .38 special loads in the same gun.
I think if you were shooting a smaller revolver, it would make more difference, but the big Ruger soaks it all up pretty good.
As a poster noted above, the biggest difference is the noise. The .357 lets itself be heard! There is certainly a noticeable difference in recoil, but it's not huge. If you shoot .38 okay, .357 will likely be no problem, unless you are shooting a light-weight snubbie.
If I plan to shoot lots of .357, I use a bicycle glove (leather-padded palm) to soak up a little more of the recoil. It's not really needed for the GP-100, but it may be a big help for lighter guns.
