I say BOTH, depending on the audience (some people won’t know what you mean if you use one they haven’t heard). And it depends on how tired I am…
I think it should be Mogue, quite simply, because it is the correct pronunciation of a great man’s name. If it were simply a made-up word for a synth production company it wouldn’t matter, but that is not the case. With that in mind, Mogue it is - only cows can say Moooog because they don’t know any better!