The 444 is definitely a hard hitter. It just so happens that I picked up a flyer at the gun show I just went to this last weekend that is all about the debate over the 444 Marlin vs the 45-70 Government. It is put out by an outfit called GREAT FARM OUTFITTERS who it appears specialize in these two cartridges.

Some of the information from this flyer:

"Introduced in 1964 as Marlin's answer to the call of sportsmen for a bigger and better .44 Magnum, the .444 Marlin reported for Duty. While the .44 Remington Magnum ruled the day as far as handguns were concerned, it's lackluster performance on game larger than deer left hunters cold. Big game hunters liked the idea of the large caliber and heavy bullets but the .44 Magnum just didn't have the steam to consistantly put down moose, elk or other large game. Enter Marlin's new .444. Loaded to 42,000 cup, this bigger and badder .44 caliber cartridge routinely spit out the same bullets at 400 to 600 feet per second faster than the .44 Magnum. The resulting increases in knockdown power were just what the doctor ordered.
Though the current limelight is on ultra-long range cartridges that seemingly beam across zip codes, the mighty .444 Marlin shines through in the deep, dark timber like few others. Combining the lightning fast handling of the tried and true lever action rifle and astounding close range power, the big Marlin can take down the biggest and most dangerous North American game, right where it hides. In Buffalo Bore's "Heavy .444" loadings, the .444 develops more than 3,000 ft/lbs of energy, dishes out Taylor Knockout Formula values that equal .375 H&H Magnum levels and has been successfully used to take big game as large as Kodiak Brown Bear and African Cape Buffalo."

They offer the following information for the 45-70 Government:

"When the U.S. military developed a new cartridge for the 1873 Trapdoor Springfield, little did they know that they were creating a legend! Consisting of a .45 caliber bullet weighing 405 grains and 70 grains of powder, the new 45-70 Government came into being. And although black powder, early rifle design and metallurgy of the time kept chamber pressures and bullet velocities low, the big 45/70 spoke with impressive authority on large game. It's big lumbering bullets just plain walloped moose, elk and bison.
But as formidable as the 45/70 was in the days gone by, today's 45/70 hunter has loads available that make the old loads pale in comparison. Designed for modern manufactured rifles in good condition, Buffalo Bore and Garret Cartridge have unleashed new ammunition capable of putting the most dangerous game in the world down for keeps. Buffalo Bore's "45/70 Magnum" ammunition, the "hottest" currently available, develops over 3,500 ft/lbs of energy and Taylor Knockout Formula values that exceed the brutal .378 Weatherby Magnum!
However, because the 45/70 Government was originally designed as a black powder cartridge, todays 45/70 shooter needs to be aware of the different power levels that are listed for the cartridge.

LEVEL I Loads that are 28,000 cup or less. (Federal, Remington, and Winchester load to 20,000 cup; Cor-Bon loads to the level I max of 28,000.) These loads are suitable for use in all 45/70 rifles in good condition-with the Cor-Bon load on the edge.

LEVEL II (Buffalo Bore and Garret loads) Loads that do not exceed 40,000 cup. ONLY for use in post 1972 lever action rifles and single shots.

LEVEL III Loads that reach up to 50,000 cup. No commercial ammunition is loaded to this level."

They go on to list the following Taylor Knockout Formula values:

"The level I 45/70 loads develop:

Federal and Winchester 300 grain loads-36.9
Cor-Bon's Best-43.7

The best .444 Marlin Buffalo Bore load (335 grain) develops-41.6

The best Level II 45/70 Buffalo Bore load (430 grain) develops-54.1

These compare to the 30-30 at 18.5, the 30-06 at 21.4, the .300 Win.Mag. at 24.9, the .338 Win. Mag. at 32, the .375 H&H Mag. at 41.6, and the .378 Wby. Mag. at 47.4."

I don't know if all that helps or not but I found it very interesting.