The best is what I've got... HD Grafx branded version 1 that's been
RGB bypassed.
The model 2 with a MegaAMP has better video then a stock version 1 and should have the same audio...
But bypassed is where it's at, totally removes any/all jailbar/rainbow effects (which is interference created by the onboard Sony CXA encoder).
Now when talking about a 32x setup, yes I would say the model 2 with a MegaAMP is better.
The bypass effects the 32x overlay centering and distorts the picture, simply put bypass CANNOT easily be used in conjunction with a 32x.
Thankfully the 32x library of games is awful, for example...
The worst port of Doom (enemies always face forward and in fact have no frames of animation present to face any other direction).
First (of what would become many) horrible Sonic spin-offs in that Knuckles "rubber band ring" game.
Night Trap Enhanced version (requires all three Genesis+CD+32x) that looks on par with the 3DO version but has censorship (released post Liberman hearings) and new/reshot opening.