Body shape and neck aesthetics. The DJ has binding and block markers, I believe. The JO has a traditional looking neck. I think the DJ had Aeros pups and the JO has Fralins. At least the older models did. Not sure if both are using the new Lakland pups now. I'm not a Lakland expert by far but I plan to be. I love my JO5 and plan to get more from the Skyline series.What is the difference between a DJ and an JO anyway? I didn't have the opportunity to try a JO when I bought my DJ4