after a few days with the R4YS and EMx 500 i can say i like the sound of the EMX500 better . it has a certain vibrancy which the R4YS lacks although being similar in sound signature
I ordered R4Ys due to my right side of EMX rattling. I did manage to fix it and it doesn't rattle but bass gets distorted more on the right side now. I never fully understood why MX and PK type shells are popular given that the drivers required for them are not enclosed, the front plastic keeps the membrane in place - a design flaw imho. You should be able to extract the driver out of it without keeping the front cover which is not connected to the driver except when it's glued to it. IEMs almost exclusively use enclosed drivers which protect their membranes while earbuds almost exclusively don't, very strange.