I honestly believe that if you bought both rifles, Marlins in .357 mag and .44 mag, and then shot them for a year, you would find that after a year, you would almost quit shooting the .44 mag and would be reaching for the .357 mag every time. After a while, you would sell the .44.
The reason I say this is that for 99% of the shots you would fire, (target shooting, plinking, predators, etc.) the .357 is much more pleasant, and far cheaper, than the .44 mag. Sure, the .44 mag has an edge in deer hunting. But, how many shots do you fire at a deer each year? One? Two? Maybe Three? And because of those three shots, are going to go with a more inconvenient, expensive, and hard-kicking round for all of your other shooting?
The .357 Mag, out to 100 yards, is totally adequate for deer, assuming that you use a 180 grain factory load designated for deer hunting. Not powerful enough? Well, then go online and research Garrett ammunition company, and perhaps Buffalo Bore company, which I think sell .357 rounds loaded to the max, and actually give you a factory round that has 90% of the power of a .30-30. Sure, these high energy rounds are expensive, ($45 per box?), but how many of them are you going to fire in a year? Ten to sight in, and 3 at deer? These rounds are stated to be safe in Marlin .357 mag lever actions.
If you have any doubt between the .357 Mag and the .44 Mag, go for the .357 Magnum first. After shooting it for a year, then see if someone will let you shoot their Marlin .44 Mag at the range. After you shoot a box of the .44 Mag, you will lose all interest in buying one. You will say that your .357 is just fine.
Hope this helps.
Mannyrock