I am not familiar with the 45-70. I know that when I was given a 444 for Christmas, there was no such thing as a 45-70 in a modern gun. I still have that old gun (1972), and I have three others. It is neat to see that the modern big bore craze was started with the humble, and yet most capable of them all, the 444 Marlin. I own four 444 Marlin rifles, three of them are the old 38 inch twist and one is the newer 20 inch twist. I have a preference for the slower twist as I feel it is more versatile. The newer, faster twist rifles are capable of shooting heavier bullets, but I question the need for extreme weight (beyond 350 grains).
The 444 is versatile. But this round is subject to being cast typed into the highly specialized, big game, short range only category. To my way of thinking the 444 Marlin is one of the most versatile hunting tools you can own today. I have sold all of my black rifles, surplus rifles, and ammo because I realize that the 444 Marlin outdid them in several areas, namely because it can be fed with such an incredibly vast array of fodder. And it can be loaded with almost any powder, including black powder in the pinch of circumstance, or even fast pull down powder. The 444 can be a shotgun, a round ball shooter, pistol bullets, and bullets up to 350 grains.
For some reason I have concerned myself with the idea that a rifle should be capable of doing all things. This is no small task. I feel that the 444 Marlin, probably the most stereotyped round in modern existence, can be the most versatile and useful tool in your gun cabinet. It can be used to kill pheasants with your shotgun load, and moose with your 300 grain bullet.
I love 44 magnum revolvers, and for a time thought that small carbines in 44 mag to accompany my revolvers were the answer. Since that time I have become a much better, and much more confident pistol shooter. Without much work, I was able to duplicate the accuracy of my carbine with open sights with my sidearm. I have watched folks that thought they could not hit a barn from the inside and were recoil scary, able to hit a paper plate with all six chambers at 75 yards with a weekend of practice. If you think a huge and heavy handgun that weighs as much as a rifle is the answer to all problems (x frame), my guess is that you have not carried that gun through mile and mile of hill and dale. To me these massive sidearms are just toys, and not tools meant to do the job. I love toys, and ALL guns, but to pack a seven pound pistol around and exclaim its virtues at the same time must take some will of character to execute without looking like you are saving face for buying an overpriced, almost useless toy. To each his own, in my world if it can't be done with a 44 special or 44 mag with a 4-6 inch barrel, it should probably not be attempted. I still own a 336 chambered in 44 mag. It is almost new in the box. It sits along side a rare 375 Texan. These won't be shot, as I don't need to, because I have a 444!
One can chamber and fire 44 special and 44 mag shells through their 444 rifle too, but I do not like to do this. I just load a few shells to fit the 444 and it is not that difficult to do this. I used to pack a shotgun, rifle, and pistol into the bush, I now just carry the 444.