What makes using OBD2 system, so much better than OBD1

TT5.9mag said
Dion, none of the other modules are wired in to the ecu. I suspect they run off of a body control module or something like that. I’ve never researched any further as I had no reason to want to use ABS or anything else. What I can tell you for sure is,on the stand, mine fires up and runs just fine without any of that crap. It threw a couple of trans codes at first because the insulation on the wiring on the plug was torn but once that was fixed the only code present was for evap because I don’t have a purge solenoid connected to my tank. I have maybe 2 hours of run time on the stand with multiple warm ups and all is well.

Agreed, they aren't wired direct to the PCM. They communicate off a pair of bus wires (drawing a blank on the exact name, but like a canbus). The PCM needs the ABS module only if it needs to know vehicle speed for something like cruise control, or to tell the IP what speed to display on the speedometer (the PCM controls it). The BCM is only useful to the PCM for the security measure as far as I can remember. But none of those are needed to run the motor or transmission.