Don't forget about a piggyback on a stock ECU. I'm not a huge fan but there are plenty of cases where they work well enough to get the job done.
I got more interested in Megasquirt's (hence the MS in eMS-Pro

) capabilities after having dinner with the founders, software engineers, programmers, etc. The eMS-Pro is indeed the MS1 chip but with the MegaSquirt 'n Spark/Extra firmware adding boost control, nitrous, fan control, programmable outputs, water injection...which I think is standard on MS1 now so the eMS-Pro is nothing more than a pretty box and better connectors. Upgrading to MSII is only $60-100 more and I'm not sure the latest status on v3 but it's probably what I'm going with...