Agree with DM, while the 270 can kill larger anamals the basic formula of larger caliber and heavier bullet still rings as true as it ever did. If I were on a hunt and was charged by a bear I would much rather have an 06 loaded with some 200gr+ Partitions, TSX, A frame, or Weldcores then any 270, including my 270 WSM that makes more KE then the 06 ever will. How many cape buffalo hunters do you see playing around with 3100fps zippy guns? Now how many 375s, 416s, and 458s do you see launching 300, 400 and 500gr heavly bonded or solid bullets? Not knocking the small caiber crowd since I hunt with several small calibers myself, but you simply are not going to get that shock kill effect on a mature bear like you get on whitetails, simply too much volume to absorb the pressure wave.
When truly big dangerous game is in the equation I will be using the largest caliber, launching the heaviest bullet that I can shoot accuratly. Anything less is just plain silly. Now mind you I still consider the 06 as being on the small side for dangerous game but a sure sot better then any 270.
Even the late great Jack O'Connor who was the champion of the 270 win sung the praises of the 30-06 on moose and brown bear and the .416 Rigby on larger tougher game.