Well, the Browell's mags were the 3rd gen mags and were the original mfg. of those. They have the tan followers and replaced the green ones. A while back Army decided to get rid of ALL black followers, USE existing green followers until they fail and stock is depleted, THEN replace with the tan follower mags. I wanna say something happened though and green ones are still used? I can't keep up anymore.
Not long after Brownells started making 'em, other mfg.'s jumped on board. I have some that identical to the Brownells mags but don't have any markings. All were new issue military surplus, all still in wrappers.
I looked at that BCM mag, you mean the black one that comes with the Magpul follower? $9.95? Does it have the "good" spring in it? I forget if it's CS springs or what. For an aluminum mag I think that's probably the way to go. I already have too many to go that route, I'm done. I do keep parts for mags though, springs and followers and the followers I started ordering are those Magpul followers. Just make sure you get the right ones, they make different followers for different mags and they're not interchangeable.
Personally for that price I'd just get the Magpul mags, you can usually get the 2gen mags on sale now 10 for $80 or the 3rd gen ones for around $100. I probably have a hundred of each and prefer the Magpul mags now. But it did take a loooong time for them to grow on me. Now I swear by 'em. They just work and are less prone to damaged lips, don't dent.
IF you want a stronger mag, I'd recommend taking a look at the ASC mags. Same thing as milspec, hell, they even make/made 'em for decades. But they make some models out of SS. Slightly heavier, not too much though but much stronger. They're actually the goto mags for the 6.5G. I think gunmagwarehouse is where I get most of my mags, Proven Outfitters and Primary Arms also have mags for good deals sometimes, just make sure to ask for a vet discount if that applies to you.
Good luck.