The bottom line is that a good 30 cal bullet is an effective killer. It was an awesome event when the 30-30 hit the market, it was improved when the 06 came along, & ditto for all the mag versions. I think the 308 is often underestimated for its honest effectiveness in the field, let alone a good shot with a 300 mag.
Any of the weights you mentioned will get the job done on just about everything. I would happily hunt a 300 Mag using whichever one the rifle performed best with.
If a quarry needs more killin', move into an AFrame, TSX, etc..
