First a few questions should be answered before anyone reccomends one over the other.

#1 - Do you ever plan on taking a shot at an elk or moose at or beyond 500 yards?

#2 - Do or will you practice enough to take advantage of the added energy, velocity, and recoil of a cartridge like a 300 ultra?

#3 - Do you like a lot of muzzle blast and a lot of noise?

They all have their place but unless you can say yes to all three of these questions there really is no reason for the ultra mag under 99% of elk and moose hunting conditions. While the regular old 300 Win mag may not be as "sexy" as the other two it will be perfectly adequate for the same 99% of elk and moose hunting conditions. With good reloading it can be bumped up in power very near the 300 Wea. Mag.

I personally see the 300 ultra as a very specialized elk cartridge. My vote would go to the 300WSM but since that one isn't on your list I vote for the 300 Win. mag.