Unfortunately, the Marlin website has little information specific to the YOUTH model.
Kind of sad. Remind me to call & tell 'em they're slacking.
The XS-7Y is a YOUTH model and actually 2 inches shorter in the stock for smaller folks. 40.5" instead of 42.5".
I do feel they should have just made an adjustable stock model for YOUTH instead of just a shorter stock.
The XS7 & XS7C (camo) are 42.5 inches long total. Regular-sized for regular & large folks.
Personally, I'd go with the .308 or 7mm-08 in the XS7.
Or in the XL-7, .30-06...but after you've fired the XL and enjoyed it's substantial recoil pad...you may never pick up your Garand again
Benefit of reloading Just One Caliber...HUGE. Monotonous...but you literally don't have to deal with switching your setup...BIG BONUS!