Skaterbrain, WELCOME!!
Truth be told, for what you have written, (How you will use it) any of the three will work perfectly well. One is no better than the other. Anything more is personal preference.
My personal preference, of the three you listed, lies with the 45-70 and here is why.
Loader or not the 45-70 is available with lite, medium or heavy loadings. If you are a loader, components are readily available, many have experience with this easy to load cartridge. Price is reasonable for loaded ammo and most components. even more costly are no more expensive than any cartridge is to reload for. (Primers for instance.)
With 444, factory loadings are more scarce, more expensive and do nothing more or less than the 45-70 can. For the loader, components like brass are scarce, bullets on the lower end are same as used in the 44 mag so they are available. But the 444 is head and shoulders above the 44 mag so its bullets need to be a bit better. Those bullets are not on everyone's shelves.
With the 12Ga, its proven to be a great shooter in USH trim. I have two and both are excellent shooters. (My 12 is a one hole shooter and my 20 is near an 1 1/2" at 100) My lite 12 ga rifled barrel was more of typical slug barrel accuracy. Say 4" at 100, adequate, but not really confidence inspiring. While reloading of slugs is doable, most done do it as in most cases, you need to make your own projectiles. The cost of fancy slug ammo is restrictive.
Good luck,
CW