I found both a Mju I and Mju II in a flea market for 3bucks each from old people. The Mju II looks like it has never been used at all and the Mju I has some light scratches over the whole body.
Going to flea markets really is worth it aslong as you avoid the turks that want way too much money for the crap they sell and probably have stolen somewhere.
Had a Mju I previously until I broke the rewind, I much more prefer the Mju II, it seems to work way way faster, didn't have a problem with it not shooting once, it looks slick, it feels very high quality compared to the Mju I and it is way more discrete.
I don't see how the Mju I would be better, it just feels like the Mju I is tougher.
Also I'm unsure wheter to sell the Mju II which seems like it is basically new aslong as these cameras are trending. I love the camera but maybe I'd get to buy another one for a third of the price I could sell it for now.