I tend to agree with Varmint Hunter
Id choose a .30/06 because of a wider choice of bullet weights together with a slightly larger bullet diameter for the bears
and a .270 Winchester is nothing more than a .30/06 cartridge case necked down to .277 inches.
You should remember that black bears weighing up to 1,000 pounds or more have been recorded in Pennsylvania. While a good many black bears arent nearly that big, obviously SOME of em are!
Theres very few species of North American game animals that couldnt be very successfully hunted with a .30/06
especially with Hornadys light magnum cartridge which turn a .30/06 into a cartridge ballistically superior to the .300 Holland & Holland Magnum!!!
That said, a standard .30/06 loading using a 150 grain quality bullet is perfect, flat-shooting antelope or deer medicine for either mulies or white-tails while a premium bullet, like the Nosler Partition, weighing 180 grains is plenty sufficient for black bear, caribou, elk or even moose. And, if you dont feel confident in the regular loading of the .30/06, then go to the 180 grain bullet in the Hornady Light Magnum loading.
However, the .270 Winchester IS a bit more flat-shooting and is easily capable of taking black bears, caribou, elk and moose as well. Buttttttt
if I had my druthers, Id druther have a rifle in the .30/06 Springfield cartridge than a .270 Winchester.
I hope I havent added to any confusion you might have had. In the final analysis, its a close call and you couldnt go wrong with EITHER cartridge.
Oh
by the way, I dont own a rifle in EITHER cartridge, so Im not speaking from any prejudice.
Strength & Honor
Ron T.