@MichaelMc I'm 95% confident the DGX and Thermo valves come out of the same factory. They are damn near identical and the new thermo's I have say made in Taiwan on them, so with the price premium, I wouldn't buy new Thermo valves. Now I say that, but I just bought over the last six months a dozen brand new Thermo's from DGX. They were $25 take-off valves that were still sealed in the box and are for stage/deco bottles so that was mainly because they were cheap.
Old Dive Rite/Halcyon square valves. They are very uncomfortable to handle due to the square outlet and short neck, but have the advantage of the square top which makes the valves almost impossible to go out of round if they get knocked over. Not really a major concern, but it is a thing. It is not worth how uncomfortable they are to handle though. I do have a set of these on one of my doubles
OMS-old, not in stock anywhere anymore obviously, but they are my favorite. I have several sets of them, one on doubles, and a couple sidemount sets. I think they're pretty comfortable to handle, and the cap on the end means that the bungee isn't going to come off.
Blue Steel- I have some, but on stage/deco bottles and they're fine. Parts kits for them can be a bit annoying though and I don't believe they make a manifold valve.
DGX/Thermo-if I were buying new valves, I'd just get the DGX modular valves with the long necks. Easier to carry on land and easier to snap the bungee over. The DGX versions are cheap, come O2 clean etc.