Hey Rachmaninoff, I don't own or have ever played a Jem so I couldn't compare them. I do have a RG20064 and a RG2820. And compared to those the
JPM neck is a little rounder and thicker. I like the JPM neck a little better. I also think the JPM neck is a little less wide, but I didn't measure it so that could also be an eyetrick because of the binding on the JPM.
And I totally love the Pickups! The difference with the IBZ/Dimarzio's in the RG's is enormous. Air Norton in the neck and Steve's special in the bridge position. The output is much higher. Yeah I dig my JPM!