If you can have only one do everything caliber with the exception of dangerous game. No contest get the .300 wsm. The 30-06 is a very versatile caliber but the .300 wsm is even more versatile hunting caliber. I own a .270 .270 wsm, 30-06, .308, and a .300 wsm. I don't need all these rifles but I reload and enjoy playing. With today's recoil pads you can noticeably reduce recoil on all the calibers I listed. You can load the .300 wsm to .30-06 speeds shooting slightly more powder.
Don't let these creed guys and 6 mm guys try to convince you to shoot their bb guns. Bigger bullets at higher speeds have more killing power. There aren't any dangerous game guys using creeds or equivalent type calibers unless their a little crazy. But they'll argue all day that their pea shooter will kill anything at any range. Their full of chit.
