I'm not a world traveled hunter. Mostly Texas, from one end to the other, up, down, and sideways. I have owned .300 magnums from Win., Wby., and H & H. The only thing I ever killed with one was my friends steel turkey cut out that was suspended with chains at 400 meters. I shot it full of holes. Wrong gun for that job.
The reason that I never killed game with one was weight. I would carry two guns and when the time came to hunt off my own two feet, a lighter piece was always chosen. From my bench work, I know the .300s to be superior, but I do not think I ever missed out on game by carrying a .30-06, and in later years a .308, both being lighter and handier than any factory issue .300 - going back some thirty or more years.
As I age, recoil is now an issue. About 6-8 months ago, I sold my last magnum. I do still have a 9.3x62, but I have no logical explanation as to why, other than to scratch an itch.
A do it all caliber? I have killed everything from armadillo to whitetails, and from coyote to heavy desert mule deer, and the occasional exotic with a .30-06 loaded with Hornaday's fast loaded 180s. I suspect that that a 7 Mauser would have worked as well, and with today's bullets, perhaps even a .243. Seems like it does not take as much gun for women, kids, and old farts to kill stuff as it takes for flat bellied studs. Hey, I did not notice this just last week. A huntress of my acquaintance showed me a few tricks, some of them with a .243, almost fifty years ago.
Use what you enjoy,
Jack