If you handload, try NBT 125's out of a 300 Mag 4 grains short of wide open.
Hovering around 3600+ FPS.....
There is no comparison between the two.
Some guys will tell you "Well, I shoot .308 Because of ammo availabillity in times of WTSHTF...balh blah blah...."
But they don't. The only reason they do is because that's what the millitary uses, and they can't think for themselves.
The Millitary even admitted that the only reason they went .308 for the 24 wasn't because it was the best, but because they knew it so well.
.300 Mag washes out BBLS quick, matter of fact, i'm guessin that's the very reason it isn't the Armed Forces Sniper standard (They still use 300 Mags, though);;; but chances are you aren't going to be shooting that much ammo.