I've been pretty happy with my JTE aluminum magwell. There is a very slight rock on seating. I think it holds the mags in a stronger way than some of the other options. The SGM "competition" s12 mags will generally work on those without alteration, as SGM cloned its plastic magwell geometry off of those.
If I were doing it all over again on a saiga, I think I would buy or modify a magwell to make it work with the V12 mags. I think those are going to be the de-facto standard going forward.
You can tune the JTE magwell to be drop free, or tug free depending on taste. I go for a snug drop free to minimize rattle and let the mags wear in. If I dip the barrel a little as I hit the release they drop free every time, but held perfectly level on target, I would say about 80%. Just personal taste in the fitting. A little less racy, but a little more solid.
I like this magwell better than The R&R because it is not huge and long, and is about half the cost. SGM makes no sense to me since the aluminum one costs the same. Tac47 is kinda neat, but I would plastic weld some extra material on each mag to support the rib where the catch engages. I think overall their mag fitting and control layout is the slickest, but the lack of structure there is a significant flaw.