In a review at Survivalblog, "Zorro" weighs the relative merits of the WWI-era M1 Garand and the Vietnam-era M14. He opines thus:
The Garand is restricted to a 8 round en bloc clip and, the clips are inexpensive. Many clips can be purchased for a hundred dollars and, they can be stored loaded without weakening anything. Conversely, the M1A/M14 has a detachable 20 round magazine which is expensive (around $25 to $40 each). Besides, the magazines need to be rocked into place and, this can be fussy for the unpracticed.
The M14's magazines won't seat if you don't load them correctly. And this is a point in favor of the Garand. Which will injure your thumb if you don't load it correctly.