I chose 7mm to split the difference between 270 & 30-06 (7mm Rem Mag & 7mm-08). But that's me.

I'd pick the 270 over the 30-06 since I tend to prefer a flatter shooting cartridge but realistically both are great choices.

I'm sure many bears have been taken with 30-06 but if I was going after Grizzly I'd want more gun than a 30-06.

Enjoy your new rifle. Don't forget to budget for a good scope...they're spendy.