First, read the Mag FAQ.
I have personally used:
OKay, which are also Colt, which are aka NHMTG (New Hampshire Marketing Group). DO NOT pay a premium for mags just for the Colt name. Not when you can get exactly the same mag with Okay or NHMTG markings.
Labelle, which became General Stamping, which became D&H. Labelle made mags with gray moly dry lube finish (the milspec finish) as well as both gray and black teflon finishes (far superior!). Labelle made mags for Bushmaster with floorplates marked Bushmaster, BFI, and Quality Parts. Labelle made mags for DPMS, also marked Panther Arms and Defense Procurement Manufacturing Services on the floorplates. They make mags for other companies with their floorplates, and I even have some Labelle mags with blank floorplates, still new in the bag with the government part numbers and such, and the bag is marked Labelle.
Parsons, which became Adventureline which became Center Industries. I have all three in my stash of mags. Like Labelle and Okay, good mags.
D. L. Sanchez. This is almost a problem... D.L. Sanchez mags originally came with the same black followers as everyone else used at that time. There were a few reported cases of malfunctions. The green "antitilt" follower was developed, and no more problems with Sanchez mags.
Go back just a little earlier... Cooper. Coopers are the only USGI mag I would really advise to avoid. Cooper was the only mag manufacturer to lose their govt contract due to quality issues.
Though I never saw any, there were some Coopers with only 3 spot welds on each of the front and back seams. There should be at least 6 on each seam, and you will often see 9 spot welds. Even with the Cooper mags having 6 spot welds per seam, EVERY Cooper 30 rnd mag I saw would not feed more than 22-23 rounds.
About 1987-88, just after Cooper lost their contract, a gazillion Cooper mags were dumped on the civilian market. I remember ordering mags from three different suppliers, and all sent me Coopers. (Yes, about 20 years ago... I've been doing this for awhile.)
What I finally determined was that the springs were weak. I could get 100% feeding if I put a plywood spacer between the spring and floorplate, of course, reducing the capacity to only 20 rounds, but the spring tension was increased. The mags would feed 100%. No doubt... weak springs.
(NOBODY sold aftermarket springs or followers back then. Why? You could buy a whole NEW USGI mag for $7-$8 any day of the week. And you could buy perfectly good used USGI mags at gun shows for $3 or less.)
I am convinced that if Sanchez had problems it was with some weak springs possibly from whoever supplied Cooper, too.
I am also convinced that the green follower is a band-aid fix for what was really a weak spring problem. I've shot many mags with black followers and no problems... and they had good springs.
The Cooper springs were so weak that if you could get a last round to feed, the follower did not have enough spring tension to trip the bolt catch on the last round. That's what we call "a clue".
So, just to be safe, with older mags, check springs first... and by comparing to new, known good mags, you will quickly develop a feel for how much resistance you should feel when you depress the follower.
If you have black followers, it won't hurt to replace with the newer green followers. If you want to spend more on other aftermarket followers, be my guest. But I would rather have old black followers with good springs, than the latest and best follower with weak springs.
I have a number of D. L. Sanchez mags now, all with green followers and good (mostly new) springs. And they work just fine.
Back to the beginning... Okay, by whatever name, D&H, by whatever name, (edited to add) and Center, by whatever name, are all good, "top drawer", mags.