300 Win mag. I have seen more velocity from the 300 win over the WSM. I load long bullets and do not want to fight the shot action WSM for room. The 300 win is near and dear to my Heart. The accuracy of every one I have ever loaded for was awesome with minimal load work. There will always be one in my safe for an all around carry rifle and long range freezer filler to past 1000 yards
222, but the 223 has cheap brass and killed its older brother off
As far as the 30 cals', I'd go with the 300win (long) if you don't care that it is belted, and the 300 rum if you do. Most of the 30's bigger than the '06 are **** good rounds and you are really comparing different apple varieties when you disparage one with another. Some guys have had better luck with one or another, and that's about it. The bigger you go, the more your barrel life diminishes, but you'll still get fair barrel life from the rum and the 30-378 roy. It simply doesn't matter a hell of a lot if your rifle is built well at all.