One thing to think on is the intended purpose of each weapon.
The M1 Garand was an infantryman's rifle, it was the #1 priority for the men on the front lines in most cases and was not favored by those who had priorities above being infantry.
Enter the carbine, designed to be something between a pistol and rifle. Easier to carry, easier to maneuver, not focused on long-range shooting. The M1 carbine is in some ways the PDW (personal defense weapon) of the era it hails from, a job now fulfilled by submachineguns and extra-short carbines ... the long gun for the poor slob humping radio gear, tending to machinery, or herding supplies.
So, if you had to consider using one of these venerable weapons in a serious setting ... will it be as an infantryman with supplies delivered regularly, or will the rifle be one of many things you're trying to do at once?
Personally, I imagine that I'd be running infrastructure and in need of a PDW, not front-line infantry.