I'm going to say it depends on the rifle/stock/etc..
My .340wby whether shooting 200-275grs kicks less than my .300 win mag shooting 180grs and thats with a muzzle break vs. without one on the wby!
300 win mag
browning a bolt
wood stock
muzzle break
thin solid rubber recoil pad
340wby
synthetic stock
pachmayr recoil pad
no muzzle break
the 300 RUM does hold/burn more powder though to get the same velocities as a .300wby...least by factory loads...more powder more kick is a pretty general theory...
my .270 is a puppy in terms of recoil compared to my .300win mag, not sure how much diff a '06 or 7mmrem mag would be...
off a bench neither of my mags is fun to shoot, shooting more than a box of ammo is annoying, in the field though who notices any kick ever? especially standing...
If you have a 7mm Rem.Mag. already I think I'd want something more than a .300win.mag. too close IMO...
I'd start at the .300wby or RUM and think about even a .338win mag or .340wby, or even .338rum though I hear that kick is particually brutal...like a .378wby...