The problem with heavy bullets in the .44 mag rifles has been slow rifling twists which fail to stabilize the heavier bullets. The Marlin .44 mag rifle has a 38" twist, and the M-94, according to recent catalogs, has a 26" twist which does better with the heavier bullets.
Marlin changed the twist on its .444 rifles from 38"to 20", according to the latest Marlin on line catalog, but maintained the 38" twist on the .44 mag. I have read articles which reported key-holing with heavier bullets in Marlin .444 rifles with the older and slower 38" twist. I guess someone at Marlin got the word.
By contrast, most .44 mag handguns are 20" twists.
I like the Marlin .44 mag, but chose the Winchester M-94 because of the faster 26" twist. My M-94 is a jewel. Accurate and reliable.
Hope my explaination helped you.