Good old 300WM. This is how I see it:

300 Weatherby - PRO - velocity, CON - $$$ factory ammo, ammo availability, brass, recoil

300 RUM - PRO - velocity, CON - Not much choice in brass, recoil

300WM - PRO - Ammo everywhere, versitality in bullets compared to WSM, many brass sources

300WSM - PRO - short action, efficiency, CON - can't optimize heavier bullets without a custom gun

Personally it came down to the WM or WSM. I hate brakes and I shoot a decent amount, so I did not want to put up with the recoil of the larger cartridges. They only give incremental range advantages over the WM anyways, if I need to shoot further I will be forced into getting a brake and would go to a 338 at that point.