Monster PRO Gold VS Pro Copper

You're better off doing a search on your question as there many duplicated threads with answers.   Here's my brief: both are good; if you want more bass and musical signature, go with the gold; for more neutral and analytical, go with the Copper. 

Golds are warmer sounding with more bass ,yet the midrange sounds more natural to me if you do not mind the added warmth.

Coppers are a more sparkle and treble extention ,the midrange sounds a little unnatural or stretched for want of a better word to avoid the warmth of the golds but this has the effect of bringing out more details in the mids.