But, in this case, it is the Superman of Earth-1 (the one who was Superboy and a member of the JLA), and the Superman of Earth-2 (the one who started his career before World War II and was a member of the JSA), having their first one on one team-up, in Superman Family.
Time to take a look at what they did!
Save My Friend, Kill Your World
Of course, just as Professor Potter touches it, someone is coming through....so, a short circuit happens, bringing in interdimensional menace, Krogg, to Earth-1. Krogg proves mightier, than Superman, and even airless space was of no problem to him.
Navigating his way through some interdimensional space, the Earth-2 Superman finds a spacial rift to Earth-1....and arrives just in time as Krogg got back to the JLA Satellite, intent on destroying the Transmatter Machine and Professor Potter, so he cannot be exiled again (like an old wizard did long ago)....
A Phoenix Of Steel
Superman of Earth-2 doesn't have any better luck against Krogg...who leaves the JLA Satellite, heading to Earth below. The Earth-2 Superman rescues the Earth-1 Superman from space, and Professor Potter suggests they need to combine their power against Krogg.
The Superman of Earth-1 muses philosophically at the end....pledging to keep a bit of distance from his other dimensional duplicate because they were just a little too close for comfort (who actually was busy at this time in the 1970s All-Star Comics revival with his cousin, Power Girl).
seventh JLA/JSA team-up (where they looked very similar, and powers were about equal), worked together against Solomon Grundy in the ninth JLA/JSA team-up, and had a massive team-up well after this story in DC Comics Presents Annual #1 in 1982 with their respective Luthors, as well as a flashback to a time when Superman was Superboy and Clark Kent, as explained in two issues of the New Adventures of Superboy....all before the Crisis On Infinite Earths.