At the end of the day this is kind of a moot point as far as deer hunting is concerned, unless you are really trying to reach way out there. To me, these are both 500 yard hunting cartridges, and either will kill any Deer out there at that range.
I've killed many animals from big bodied Muley bucks to Cow Elk with a 257 Roy, using various bullets from 100 gr Nosler BT at 3780, to 115 TSX at 3450, they are all dead. I also killed the biggest bodied Buck I've ever seen with a 6.5 CM and a 123 Amax, neck shot=DRT.
Pick whichever you like, and have some fun finding that magic load!