I had a Contender barrel in .44 mag and didn't think it kicked that bad. What WAS untolerable was the 45/70 barrel however
My experience is just the opposite. It depends on the barrels. I have a 10" octagon .44 Mag, and a 14" ported .45-70.
The .44 is rough. It has more recoil and muzzle flip than any other .44 mag (revolver or auto) that I have ever shot. That's mostly because it is lighter than repeaters. I only shoot one load from my .45-70 (so far) a 400gr cast, at normal factory spec (black powder) velocity. It is a handful, and quite stout, but doesn't seem as "sharp) as the shorter, lighter .44 Mag.
Recommend getting the full rubber Pachmyr grip if shooting hard kickers.
As to why a handgun? Lots easier in a tree stand. For your friend, whichever caliber he chooses, I would also recommend a rest (shooting stick, etc.), and then just hang on. One shot is all you get, so there is no need to "control" the recoil, other than not letting the gun drop, or hit you in the head (which I have had a friend do shooting my .45-70! Wacked him in the nose with the edge of the red dot sight! Bled a bit.
Get a good dot sight, if you like that kind of thing. Scopes are ok, but at woods ranges, I don't see much advantage over a dot, and the dot has some advantages over regular crosshairs, especially in dim light. If you like the iron sights, recommend some model paint in contrasting color for the sight (red, orange, bright green, etc. White is ok, but if hunting in the snow, not so much. Model paint lasts a fairly long time, is easily touched up, and cheap. Wife's fingernail polish works too, if found in suitable color. Degrease the metal before painting, for better adhesion.
You can also get the grip/forened fitted with sling swivels. Being able to sling it while climbing is a plus, unless you have a chest type holster.
Deer are not armor plated, contrary to what one often reads on the internet. Regular full house factory .44 Mag will almost always go competely through. Can't see any use for more than that.