Hi again patracan,
I cannot comment on the D3 build quality, but can honestly say the build quality on the HOG 2nd stages is superb, so I suspect the 1st stages will also be good.
Oh, and I believe the HOG D3 is DIN, the Mares MR-22 can be either DIN or yoke, depending on what the dealer brought in? Mine are yoke.
If it were me, I'd be left again with a decision on which style 2nd stage I preferred.
I'm not sure on the warranties. My personal and very jaded opinion is that I see all regulator warranties as essentially worthless. Neither of these regs are going to have "warranty recalls" at this point, they are well-established designs. To maintain the warranty you are generally forced to bring the regulator in for annual service (parts are free, labor is not), whether that service is truly needed or not (but that is a another argument entirely
). This is true for many manufacturers, I'm honestly not sure about Mares and HOG since I service my own gear.
I would probably lean towards HOG, despite my infatuation with Mares regs. I do believe the D3 comes with or without a cold water kit, I would need to check... maybe the model on sale does not have it??
Have fun with whatever you decide, there really is not a
bad choice here. Both are good regs.
Best wishes.