Absolutely no question whatsoever that you should get the .44 Mag. The factory ammo is much much cheaper than 45-70, and it will easily handly any deer or hog out to 100 yards. It has much lighter recoil, much less noise, and is a pleasure to shoot. Ammo can be found anywhere, and it comes in an extremely wide variety, from self-defense loads to big game loads.
Don't spend extra money to buy something you don't really want or need, that will end up costing you alot more money in factory ammo.
In other words, your instincts are correct here.
Regards,
Mannyrock