The MD's are good and so are the Golds and Coppers. I may be in the minority here in that I don't find any of them superior to the others. I can see someone choosing the Golds out of the 3 or the Coppers or MD's if someone had to choose one. It depends on your preference really.
It is a matter of choosing a preferred sonic signature. These are 'fun' IEM's designed to entertain your ears, not flat/neutral IEMS which might be more 'accurate' and/or 'boring'. With the proper burn-in, tip choice, and insertion they each do well with detail retrieval. However, the Coppers are the fastest drivers if you listen to ridiculously quick speed/death metal.