If it's not really about tuning or wiring. Then it belongs in here.
To start to answer this question, we should first ask, what makes a ECU fast?
i have been asking myself this sometime now. So of the ECUs we have access to, who is the fastest, why is it faster and how important is it?
I guess you have to define "Fast" first. Is it the amount of time that the ECU takes to complete one loop of the code? Is it if the code can deal with a 60 tooth crank wheel at 15000 RPM? Some of this depends on how many features you have turned on. For example, a V12 on full sequential fuel and spark on a 60 tooth wheel, VVT, traction, knock and boost control is more processor intensive than a basic batch fire setup running a 4 cylinder.
Bottom line is later designed ECUs are more commonly based on newer and faster, automotive specific chip sets.