Re: 375 h&h or 300WM ??
I've owned both before I sold off my 300 WM. Frankly, I've found many different standard
cartridges do very well out to 300 yds or so, and had a 270 Win, M70 rebarreled to 280 Rem
for the animals I hunted with the 300 WM. There are other standard cartridges that one can substitute for any of the 7mm or 300 mags and not lack anything worth discussing when hunting.
As for the 375 H&H, shooting the 270-gr bullet, it has a very similar trajectory as the 180-gr
out of the 30-06. The 375 H&H works well on all bears, elk, and moose with heavy loads, and very well with nominal meat waste on smaller game animals when loaded with lighter bullets than either a 7mm or 300 mag.
Sometimes discussing ballistics, bullets, & cartridges overlooks some "other" equally important
considerations when purchasing a new rifle or cartridge. Such as are you sensitive to recoil?
What is the typical distance you shoot and collect most of what you're hunting? Are you hunting
in an area that grizzlies have recently (last 10-20 yrs) moved into? It's not that a 7mm or 300
mag "can't" dispatch a grizzly, just that the 375 H&H, loaded with a premium bullet will do it
with more authority.
If you're interested in hunting at longer distances, those cartridges tend to have a bit more
powder capacity than either the 7mm RM or the 300 WM; and, shoot 180/190-gr & 210 gr bullets,
respectively, and still have sufficient velocity to humanely kill the animal at extreme distances for hunting.