Allen has been great in sending me service literature (service manual stuff) in pdf
Interesting to hear that as the previous common knowledge was that Allen only supplied service lit. for analog organs. If they are now supplying it for MOS & ADC organs, that's a good idea. At any rate, what I was told by a tech is that the service lit. became progressively less useful. (other than, of course, things like voicing charts) By the end of the ADC era the techs were expected to do very little hard field repair at least to the boards, but just to have a suite of standby boards to swap for replacement. Certainly someone skilled in electronics would not need schematics to repair fairly standard things like amps and power supplies.
I think the ADC-4300 would no doubt sound better, it had many more DACs overall, feeding more real channels of analog audio that were then mixed down to 4 channels. With an 8 bit DAC having as many as possible helps hide the limitation of the quantization scheme. It was also the later MADC-3/TG-10 era with more realistic chiff, though that is more helpful in a large acoustic setting like a church. Overall pretty similar though...they both had 4 final output channels....the 4300 probably has a sub crossover which will help with bass, I believe it needed that as it had a 32' stop.