It's a very strong caliber for big game. A lot of people love it because it shoots a 30 cal. bullet very flat, very fast and kills game quickly. It does have a lot of recoil and noise to me. Good for most plains game and North American game or sheep hunting in the many other spots around the world.
So I have not missed my decision.
If as you stated in another thread you're holding your shots to 400 yards or less, you're not going to have a problem with the .300 Win Mag and your decision is fine. The .300RUM's speed advantage does not in my mind become an advantage until at least the shot distance has gone to beyond 400 yards.