Both caliber's and have been around for a long time. I own a .270 Remington and think very highly of it. It's been a highly effective elk rifle for me. Not knowing your hunting objectives I'll take a guess that bear is on your bucket list. Most noteably Kodiak or Brown bear. If in fact that's the case, I believe I would opt for the .300 mag. Little bit more power to it's punch. Good rifle's though, both of them. Good luck to you!