I would take which ever one you shoot best and feel the most confident with.
I took a coastal grizzly here in BC with my 300 Wby Mag loaded with 220gr Nosler Partitions. I shot it broadside at about 85-100 yards, the bullet passed through the bear, and he was knocked over but got up and ran about 50 yards into the bush where he lay down and bled out.
My friend is going sheep hunting this summer and he is contemplating whether to take his 6.5x55 which he is the most confident with or 8mm Rem Mag which he just picked up. The other guy is taking a 300 Wby.