Build quality of SM3 is questionable. However I think that the build quality of EM3Pro, or any other custom IEMs, should be better than SM3. If I am not mistaken, the shell of EM3Pro is made from hard acrylic with silicone filled inside the shell, protecting the drivers and increase isolation as well.
The EM3pro build quality is superior than the JH's. They feel more solid (as they are solid), the fit was perfect on the first time and the acrylic cast looked better; plus the cable connection is recessed.