The 375 H&H cartridge will always have the nostalgia and historical emotions with it. I have a few of the rifles and nostalgic feelings for it. But, the 375 Ruger had my attention as soon as I was aware of it. The concept of a off the shelf or re-barreled rifle, with the same action as my 338 Winchester, with the same or slightly better ballistics, seemed good to me. I have no regrets with the cartridge.

I can say the same regarding the 416 Ruger, action fit, and no regrets. It might be a little less velocity than the 416 Remington with equal barrel lengths, but serves the same role. A little less psi, powder, and COAL. Without doing the math, I would guess 75 fps on the average, in favor of the Remington version. I am not going too excited over even 100 fps. Particularly when the 20" Ruger version will do 2500+fps with 350 grain monolithic bullets.
I am not bashing the 416 Remington. I think the 416 Hoffman and Remington are great rounds. I have a M70 416 Remington, stainless re-barrel that I like quite a bit. I do recall some of the 416 Rigby nostalgists, seemingly offended by these cartridges.