The 444 Marlin came out in 1964.
"A 45-70 will do with a 400 gr bullet, what a 444 will do with a 300."
A 400 gr at 2000 fps will have about 50% more recoil than a 300 gr at 2000 fps.
A 45-70 will drive a 300 gr bullet faster. A 300 gr bullet from a 444 has a higher BC and SD, so
at the same speed, a 300 gr 444 will have a flatter trajectory.
45-70 is more available, with more selection.
Paying $40-50 a box gets old really quick. A Lee reloading kit will pay for itself by the third range trip (or earlier

)
Reloading gives you many more options in both calibers. Better selection for the 444, and ammo more powerful than you can stand for the 45-70.
If a hit from a 444 doesn't knock it down, a hit in the same spot from a 45-70 probably wouldn't, either. Seriously, bullets of 265 gr and up are
BIG. The difference between the two is about the difference in being hit by a Freightliner or a Mack.
You really aren't going to go wrong with either. The 444 vs 45-70 arguments are some of the silliest on the internet. Both have big bullets that hit hard.