The 375 H&H has long legs. I am an unabashed lover of the 1.5-5x Leupold, especially on a rifle the could see close cover work on large game. That being said, the nominal 4.5x top end on the Leupold fails to make the most out of the potential of the 375. Now, I'm looking at this through the lens of a multi-species hunt such as you encounter in Southern Africa where your quarry can range from animals the size of a purse-dog up to one that dwarfs an Alaska-Yukon moose. I feel completely confident in hitting an eland or moose at 300 yards with the 1.5-5x from a field rest, but if you shoot one of the smaller animals, even at 100 yards, you run into reticle subtention issues (especially with a heavy reticle like the "heavy duplex". Obscure too much of the vital zone and it can make accurate shot placement more difficult. That is when I would tend toward the 2.5-8x Leupold as it has a great balance of overall size, weight and power (the 3.5-10x might be even better but I have an illogical and almost inexplicable hatred for 40mm objectives on hunting scopes).
Now, in North America you likely won't run into that issue since most combo hunts you go on won't have that extreme range of animal sizes. Maybe Moose/Caribou/Mountain Goat but that would be the extreme of it.
Bottom line: If you're happy with the reduced magnification and the associated limitations then look at a 2.5x/3x/4x fixed or a 1-4x/1.5-5x variable. If you think you'll want more scope then look at a 2.5-8x or 3.5-10x.