[NoDOHC]

I did megasquirt on a motorcycle. It used an 8X8 map (manifold pressure vs RPM for fueling and a similar map for ignition advance. The ignition trigger is a little funny (may need to tweak resistance on the on-board filter). Basically, it is the simplest, quickest and easiest ECU to tune, probably the hardest to set up (unless you get some canned maps). The global injector trim feature is awesome for global richening/leaning after adjusting fuel pressure.

I would say that compared to the microtech, a megasquirt is simple in every way. I would argue that Haltech setup is easier (they even include a rotary setup section in the help file). I can also tell you that you get either idle air control or ignition control (Unless they fixed that in V3) on a megasquirt.

The big downside to the megaquirt is the lack of fuel mix vs. air temp maps, fuel mix vs. coolant temp maps and ignitiong timing vs intake air temp maps. Basically, the megasquirt can adjust based on these values, but it only uses a linear formula.

In a nutshell:
Microtech = Really expensive, Complicated setup to get running, amazing adjustability once you get it running
Haltech = Pretty expensive, Simplified and easy setup, good adjustability once running (only missing the ability to run negative split on E6X).
Megasquirt = Less expensive, complicated to setup and get running, limited adjustability once running (although I think you can run negative split).

Unless you are a really big fan of the open source nature of the megasquirt, I would go with a Haltech (that is actually what I did).

The choice is still yours in the end. Do some research, download Halwin and the megasquirt software (megatune?). (I don't know if the microtech software is readily available for download or not, I only fooled with it on a friend's car.)