(the 7mm Rem Mag )... Surely a nice cartridge for a more-or-less dedicated mid to long range rifle. If you are looking for a multi purpose rifle you are also going to use on driven hunts I'm not sure what sort of advantage you would really have over a bit milder 7mm.
That is my thinking, and why I have a .280 Rem with 22-inch barrel, a 7x64 in a 20-inch fullstock Mauser, and two 7x64s in 23.5-inch rifles.
The 7x64 / .280 has 100 yards over the 7x57 in terms of energy. It really can do a lot more with the 160 and 175-gr bullets than a 7x57 or 7mm-08 can. If you are hunting large game at closer ranges, such as boar, bear, and moose, the 7x64 has all the power you need, vs the 7mm RM, and less recoil, faster second shot, etc. With the 140-gr bullets, the 7x64 shoots like a .270 Winchester.... or you can load it mildly like a 7x57R.