Any 20 you test and find is reliable then will work for you. There are preferences by maker over the years but the real issue is that picking up used one on sale at gun shows, etc all too frequently results in getting a junker that might well have been better off crushed.
Even then those who appreciate the older mag bodies know a follower change, new spring, and some careful realignment of the mag lips to factory standards can fix those old workhorses. There is also the political implications of destroying a mag body that was pre ban or potentially so now. Once it's gone, it's gone forever.
If you do run across a mag or two that simply won't work at all for you - time to trade them off with a disclaimer of their function. Others can and do knowledgeably pick them up, and if it's still an issue, then strip them down and sell them as components only.
A lot of M16 users carry a 20 round mag up front, cops tend to use them in cruiser ready condition as the storage of a loaded mag in a firearm is easier. 20 round mag definitely have there place. As for the curvy D&H mags, I would be more concerned about the straight mag well on the AR as that is the initial problem. The mag should curve to a slight degree as the cartridge is tapered. We have just been getting away with it and it also goes to having to use an anti tilt follower to help facilitate feeding.
