I think the fit of the rifle and confidence of what you are carrying will matter far more than any possible difference in terminal ballistics. If the 30-06 has been your go to gun for any length of time I would grab it and not even hesitate.

If the 300 is your new woman and you just wanna break it in on an elk that is reason enough to switch.

Hunt hard, kill clean, waste nothing and offer no apologies.

"In rifle work, group size is of some interest...but it is well to remember that a rifleman does not shoot groups, he shoots shots." Jeff Cooper