Theyre both kinda similar fish with similar attitudes. Bout the same size. Different looks for sure.
As far as aggression goes, I would say JDs are more vicious and predatory while GTs are more showy and territorial. Gt can hang with a wider variety of tankmates ime.
I had a male jd now and im thinking about getting a male gt to room with him. We'll see how that works out.
I agreed up until the part where you said that JD is more aggressive . Honestly I've had both and it just depends on the individual fish. I had a JD that was more of a defensive fish he wouldn't take anything from anyone and he would hold his ground . Then I had a green terror that would not mess with JD because he was a smaller and newer to the tank , he Was so aggressive I had to rehome him. As soon as I put him in the tank though he was by far the most aggressive and he probably would've taken out the JD, that's the only super aggressive cichlid I've ever had, it really depends on the individual fish they're all pretty much in the same class aaggression though. I had another green before that one who is similar to the JD, didn't start fights but will finish them. those two got along well for a while. He passed away from a infection , great fish.