A lot of magazines for the Ar15/M16 family was sent to loose rounds this ( our first ) year for testing. In trying out new guns, I used a lot of mags from as many different mfgs as I could get my sweaty little hands on. The usual crew was of course tested, like the Pmag, the USGI mags as well. Below as my three favorite mags tested this year.
The top three in my opinion are the Tango Down ARC mag, the Lancer advanced warfighter and the surefire 60 round mag.
The Tango Down and the Lancer are tied for my all time favorite. IF I had to pick one it would be the lancer. I tried to make them both stop working in ways that stopped just short of destroying them. I tossed the both off of a 50 foot cliff loaded and they still worked perfectly. I Left them soak in muddy silty water, froze them and poured dirt into them. I even stomped on them and ran over them in my jeep. These are tough mags. I love the metal feed lips of the lancer and really feel it is the best mag on the market right now and like it more then the Pamg, I have not tried the new generation of Pmags yet. But I doubt I will change my mind about the lancer. I am sure that will stick in some peoples craw but, too bad. I know what I saw.
The surefire 60 is my third favorite. I tried really hard to causer it to stop working, I did not toss it off a cliff or run over it because I know it will not take the same level of abuse. But, I am not sure it was meant or expected to. I see the sure fire 60 as a specialty mag for matches or breaking and ambush or what have you. I think anyone who gets one for fighting would still treat it gently as the some what specialty tool it is. Now, thats not to say I was not rough on it. I was. I could not get a malfunction from doing stuff I think of as likely abuse. I poured dirt a pebbles in it, water soaking, pressure on it etc. You can read my test of it earlier this year on this site. I think most people using it to fight with will likely just have the one, and keep it in the gun and keep up with it and be slightly more gentle with it when not in use.
The surefire still has a ways to go before its gotten the same confidence of Pmags, but nothing beats having 60 rounds in the gun ready to go, without causing the gun to feel a lot heavier or un balanced. For that, it makes my list and I feel its worth its price easily. I have not tried the 100 round mag yet, but will be soon. I feel these are way better options then the Beta Cmag. The Cmag is a toy for people with NFA stuff or goofing, they are just not tough enough for real use. And I have seen the problems first hand.
The Pmag will probably remain every ones darling for a while to come. But I feel right now, the new lancers are a much better mag. and you should give one or two a serious look. The Tango Down suffers from a couple of problems but nothing that can not be over looked, It is a very tough mag and is in use by some big names. I do not use that as a guide since a couple of the big names are pretty much shills in my opinion, but it does matter to some people. The follower on the TD is a real work of art. I feel confident in saying the TD would also be a great choice if you are looking for a upgrade from the Pmag.