I normally decide what to shoot based on how it stores/fits in ammo cans.
Examples of boxes:
xm193 fed (20rd box) can fix lots of those in an ammo can. Keepers
Q3131 win 5.56 (20rd box) just like fed, very dense packing in ammo can
AE xm193 5.56 200rd bulk (thought it was 10x20rd boxes, opps)... very dense but I just don't like long term storing where brass is on brass
umc .223 50rd box (pretty dense, but is .223)
fed 100rd bulk .223 (same deal as AE xm193, but in .223)
umc .223 20rd box (way too big of a box, very few to the ammo can... temped to rip them open and dump them in a can)
I would shoot from the bottom up, but would likely skip the .223 50rd box so my .223 only rifles have something to eat in a SHTF.
Just offering a different point of view. Of course, all of these would be pretested to fully function in all of my rifles.