If you are going for long range precision go with something in the 6mm world.

If your going to do a 300 - then why not a WSM (you increase your barrel life and then you can do a short action).

There is a minor increase in felt recoil going from .308 to .300 - but put your big girl pants on and deal with it.

That said - all my 30 cal precision guns are in .308. But I think that's more of a historic reason than anything else.