What I heard they are from the same source but MQ does more case work (I might be wrong). The best way to same money, buying the cheapest case from Viet and do a little case work by master builder should be fine. BTW you seem to like Sea Dweller huh? I recently got a 1665 from one of master builders in my opinion and I really enjoyed it more than my Red Sub 1680. I love how the thick case and the crystal without cyclops look.
Welcome to the RWG club amigo!