I have hunted over a lot of the globe with a 300 WM and I really like the cartridge. I have for the last 20 years been using a 300 Wby and like it even better. I have a 300 WSM and a 300 RUM but my go-to rifle is still the 300 Wby. The 300 WM is a much superior killing cartridge to the 338 WM with a lot longer legs and much greater energy when you streatch out a bit. I would highly recommend the 300 WM or 300 Wby which is my personal choice. My 300 Wby is better travelled than most people and is a killing machine to 500+ mtrs. Either the 300 Wm or 300 Wby cannot be knocked for 95% of all your hunting needs, period. After a 300 Mag the next step up is a .375 H+H, the reality is if a 300 won't kill it you MUST have a .375 or bigger.
This advice comes from a man who has hunted and killed every size of animal on the planet from blue duiker @12 pounds to African elephant @12,000 lbs. I have some experience behind my advice. I have taken animals as large as Yukon/Alaska moose and African eland very successfully with the 300 Wby and a very large bison with the 300 WM. THEY WORK!!!! I have also taken big game from 15 mtrs to 600 mtrs with the 30 cal magnums and have the greatest confidence in them to do the job. In my opinion there isn't a better 1 caliber do all North American cartridge than the 300 WM/300 WBY. JMHO