Viltrox EF-M2 is optically identical to the Metabones in center of the shot, corners are a bit blurry. However is that worth the difference? If I was shooting a movie for the cinema, I wouldn't skimp on that, but as I'm mostly shooting for youtube and web delivery, there's no way anyone can see the difference and none of my clients ever commented on that.
I have it, I had zero issues with it and I think it's worth the price.