I too agree, the .338 ultra mag, is fine as is, but if you have your heart set on the other, then make sure you do it will a 30'' barrel to reap the rewards of the extra it has, other wise you are spliting hairs on caliber, for a lot more work to make ammo!! and buy one good barrel, its cheaper in the long run, them lower cost barrels will wear out at high vel. that that caliber will be doing!!
Have you ever look at the .338 hart caliber, shot a few and seen them in action, from
Robert W. Hart and Son Inc.
he has several hotter ultra mag copies( 7mm-300-and .338) been around for many years, and work very well, I have a 30 Hart, my self, as well as a remington .388 untra mag! but see no need to up grade to the hart, but if I was starting from scratch, I would think hard about it, but I like to be able to buy factory ammo, in a pinch!!, if it was me, I'd tell you to stick to the rem, but your money!, your call!!