I would pick the 300 WSM although both cartridges are equal to the task. I also consider the 300 Win Mag to be a tried and true cartridge. (sorry). I do see your point though. They are both balistically equal.

JUST FOR ME THOUGH, I would rather have the plague than a 300 RUM.For those who need or want the recoil of that beast, they are welcome. I have a friend who had to have one but he is scared to death of it. He has shot one box of shells in five years. When he takes it to the range to check the zero, it takes hum 20 minutes to get up the nerve to fire that one round. He says a little prayer that it stays zeroed so he doesn't have to shoot it twice. But he LOVES it.