I own both GR01 and R50, and no -- they do not sound identical. R50 is better. More engaging, layered and fun. This is not a matter of insertion and tips as I ordered Custom Art tips for both of these. Hevaily recommended, btw.
R50 have built issues, this is true. After a year or so, my pair has some problems with memory cable insertion to the headphone.
I prefer some tracks, especially with average mastering, on R50 over my full headphones, HE400. With custom tips R50 simply rock. HE400 have an edge in bass and soundstage and are more capable technically, but R50 is so fast and entertaining, also more forgiving.