The .300WM and the .30-06 are going to give field performance so similar, you'll likely NEVER notice the difference in the two (other than recoil). The .270win is limited a little bit since it's stuck with lighter bullets than the .30 bores, it's a great round, but it is what it is, it's a downsized .30-06, and can handle game accordingly. The 7mm's are basically in the same boat, but they'll kick like hell to get the same results of the more mild .30-06, and they'll still be throwing light bullets when it comes to big game.

I'm going to throw .45-70 into the mix, great all around cartridge, a little heavy for light varmints, but I don't take that to be the basis of this thread anyway.