With respect to all, I have never shot at anything with my .375 beyond 300 yards, and have never had to increase magnification above 6 power for a shot. I also don't get the need to bring two weights of ammo. I have killed all my buffalo and a truck load (large truck) of plains game all with the 300 gr bullet. One could do the same with a quality 270 gr projectile. Nothing was beyond 300 yards, and if I am really going after Vaal Rhebok, I'm probably not bringing the .375. If I am chasing a buffalo, I don't want the remotest possibility I have confused ammo and/or scopes.
I killed my first buffalo with a .375 equipped with a 3x9 variable Trijicon and the next one with Leica 2.5x10 (no practical difference from a power perspective), and the last two with a 1.5x10 Leica. The latter is the ideal scope for me, but it is expensive, and a 3x9 will absolutely get the job done. The biggest challenge is not potentially stopping a charge, but getting a second bullet into a departing animal if you get a chance. Assuming it is a good scope, the more critical thing to me is that it is instantly dismountable for a follow-up. Talley rings and bases are hard to beat.