I think the .300 Win Mag is a true American classic. It has a lot of appeal. Apart from it's shorter neck, it is a good cartridge and should be readily available in many good shops, components, dies etc.

I would also go for a .300 H&H Magnum however. Earlier and the original. Only a bit faster than a hot .30-06 but a true classic.

But I have a 8x68S and it can do every thing either cartridge can do. Bullets from 150 grs to 250 grs. I haven't used mine anywhere near enough. Hopefully I still get opportunities to use it in Africa, North America especially Alaska. Europe. Of course Australia and NZ. So doubt I'll ever buy a .300 Mag of some sort.

BUT I do have a Tikka/Valmet set of .30-06 U/O barrels. I've had interest in converting it to the slightly more powerful but lesser available .300 Super H&H Rimmed. That would be a cool option. I've got everything needed for a .30-06 but a .30 Super would be cool. A competent gunsmith would be needed. Either would make a useful sambar hunting rifle.

It would make a useful Double Stalking Rifle choice for BGRC shoots as well. And field hunting double stalking rifle.