The D-jest system is excellent and was quite amazing when it came out in 1969. But parts start becoming difficult to get and are crazy expensive new for some of them (contacts, MAP, 3.5 injectors).

Megasquirt brings a whole new dimension, as ignition, VE and AFR maps can be modified by the driver, or let TunerStudio do the job live.

In the end both have merits. I have a '72 pristine BMW CSI with a D-jet system and it is remaining this way as the car is all original. My W111 Coupe is a different story, with a 5.0 M117 mated to a 5 speed manual trans, the MS is just adding to the fun.