Cool little pieces. I guess the thing I look for is the intended function. If it's truly to use as a "survival" rifle then the stock-packed one in a pistol caliber is handy. That being it is compact, can be a single caliber across hand and long gun, easy to toss into a pack but not intended for immediate use.
Otherwise, weight and dimensions matter. Long movements with rifle and pack can be a challenge so weight matters. carrying additional .22 rimfire ammo is almost negligible if you're just tossing an extra box of 100 somewhere.
