What makes using OBD2 system, so much better than OBD1

I had 20 yrs in auto repair. Got out in 97. So I never worked on the OBD2 systems. I also have a 46 dodge truck that has megasquirt MS2Extra. So I've been involved with things like this before. Just not OBD2... or the RE series transmissions ,just looking for some input. Thanks