Here's my personal thoughts on AR magazines from 20yrs in the PPCLI and 20 yrs owning Colt SP1, Armalite M15a4, Norinco full length and Norinco M4 length, an XCR-L, and an AR180B.
Best deal I ever got- was given 20 old Thermold mags a storeman found about 5yrs ago. Wpns tech pinned all for me for a coffee. Only one had damaged lips and it fed fine. These mags had large strengthening ribs and wouldn't fit in most pouches. I gave them away to a new AR shooter.
Toughest- A shiny black steel 5/20 that I think came with the AR180B. It is heavy but feeds smooth and the short profile is handy, but like any short body, not good in tactical pouches.
Best function- my old Colt 5/20s with the metal follower, and Armalite 5/20s with the slight curve. These fed smoothest in all my ARs but too short for pouches.
Work- New bought D&H with magpul followers and ranger plates because work allowed it and my life depended on them. They work in every tactical pouch. Before that, OKay brand aluminum from the early Bosnia Croatia tours when available, or old Thermold until they wore out or broke in the Wainwright winters.
Future- PMags, whichever version I can get about 30 of. For tactical training and competition, all mags should be the same. All the little 5/20s will be relegated to shooting coyotes with XCR-L.
If all you do is plink at the range, enjoy the cheapest mags you can get (likely D&H). If you compete or train, buy a ton of PMags or D&H.
Always number your mags with paint and a stencil for two reasons. So you can identify your mags on the ground after a competition, and so you can identify faults.
Always use them in the same order, to help remember which stoppage in which stage .
If a mag gives you more than a couple issues out of the rifle you primarily use it in, crush it. You cant fix it.
Note for soldiers- Don't have any of your work mags at home. They are prohibited devices! You are not exempt! It doesn't matter if it belongs to the Army, or if you use it for work. Leave them at work! Stay out of Sh$T