First off... I have NO experience hunting elk with a muzzleloader. My one time was with a 7mm Remington Mag. BUT if I had to head out tomorrow it would be with a Barnes MZ Expander in 300 grain or a Nosler Partition on 300 grain.

The other way I would go is with one of my White rifles shooting a 460 or 500 grain Bull Shop conical bullet with 90 grains of powder under it.

The others you listed I am sure would get the job done. But as we all know, bullet placement is most important. But those would be my choices. I base this on a LOT of range time with different bullets, and the hunting reports of some very respected forum members here. If they say they work, I would take that to the bank.

On a side note... if the person hunting with me (I normally only take guided hunts so they can do all the work, and increase my odds) told me that the shots would be close and quick, I would take a .58 caliber GMB and load 110 grains of 2f black powder and a .570 roundball. Not the fastest projectile in the wood but I know it would get the job done. Also a .54 caliber roundball is no slouch when it comes to taking game as well.