I have never been able to figure out what the 444 Marlin can do that a .45-70 can't! That 1:38" twist they are showing is going to limit you to lighter bullets; i.e., this is an "Express" rifle, like the .45-90 WCF. Not sure how heavy a bullet you can stabilize, but if it was me, I'd go for the .45-70. They are calling it a "M1886/71", which the original M71 was, with a few mods. Specifically, the M71 locking lugs and breechblock have the locking surfaces slightly angled to create a wedge effect, rather than the straight vertical surfaces on the '86. The other change involved the ejector button and the face of the breechblock. On the '86, the ejector forms the bottom half of the firing pin channel. If the ejector breaks off the stem that projects back into the block, the primer is unsupported, and will back out when a round is fired.
Because of the excellent design of the original '86, you get a sprinkling of gas around your forehead, just below your hat, but no other damage!
In the M71,the ejector button is smaller and the firing pin is completely surrounded by steel. Ejectors seldom break...unless you are pounding the action with some pretty stiff loads. One solution was to buy a set of M71 breechblock and the locking lugs (you need both the block and the right and left lug), and have them fitted to the action...or, if they followed the M71 pattern, one of these new ones. Only happened once, and I had the changeout made. Also did the same to a .33 WCF '86...just to be on the safe side. There is NOTHING smoother than an '86, with the M71 right behind it!
Any word on the price?