on pa whitetail, all 3 are going to give you close to the same results. the wby will have a little more *** than the wm, and the rum a little more than the wby. a 200gr bullet is going to wreak havoc on a deer regardless of whether its doing 2700 or 3100fps.
Surely no one named Samson is worried about the kick from a little ole rifle!
Seriously, though. These calibers do recoil significantly in rifles that weigh little enough to be carried. That's why I shoot an 18 pounder with a good brake.
I watched a new friend of mine blast away with a 30-378 in a rifle that couldn't have weighed 9 pounds total. It was absolutely hilarious - his hat was falling off and his eyeglasses knocked sideways on every shot...
I recently purchased a Remington Sendero in the 300 Ultra Mag. I love it! After sighting it in I shot three rounds, 150 grn factory ammo, at 300 yards and the end result was a ragged hole. Very nice rifle. Im in the process of getting a newstock (McMillian)and a new trigger (Jewell<--sp). This rifle will become an excellent long ranger for sure!
On the .300 RUM plan on the recoil being double that of a 7mm Rem Mag. A brake will get it back down to 7 mag levels.
For consideration, the recoil of the .300 RUM is roughly the same as the recoil of the .338 RUM. The .338 has higher BC bullets, better wind-bucking, and much greater terminal performance. Food for thought. Don't want to confuse the issue though...