If it were me (and it is actually), I'd definitely go the route of ultimate control in the SM4 (Autronic). I'm not sure where OpenSource is in terms of control, but just keep in mind the customer support of OpenSource versus a motorsport ECU manufacturer like AEM, the Hydra, or even Autronic.
Another thing to consider is, if something goes bad, where are you going to turn? Just things to think about.
I'd suggest calling Pat @ Rocket Rally (he's tuned pretty much everything out there), Cam @ Lightspeed, Phil @ Element Tuning (Hydra), and AEM for info on their standalone ECU, to get as much information as you can before diving in.
Good luck with your build.