I've owned three .300 H&H's. It's a nice round, especially if you want to a traditional .300 magnum. But right now I don't own one, and probably wouldn't own any .300 magnum if I didn't have to for professional reasons.
That's a telling statement:
"I don't own one, and probably wouldn't own any .300 magnum if I didn't have to for professional reasons."
Les Bowman promoted the 7mm RM because as a guide he found that many hunters did not shoot the 300 magnums well.