It depends on your personal preference. If your mixing vinyl, the SL1210s are the non plus ultra in my opinion. In case that your M5G is carrying more dust than actual vinyl, it could be an option to sell them :D
I would never sell mine, because It was a gift from my father in law. They were used in the Club he owned back in the days. So they gained some sentimental value already.
I like to check around new communities daily, it's interesting to see what people gravitate towards, in this case, "DJ Setups" was to good to skip checking it
Random storytime: When I was 11 or so, I was really interested in some kinds of techno, although I didn't knew much. Then Christmas comes around, and I get a small DJ Mixing thing, it was for kids but I still have it