We are spoilt for choice now days with a vast range of ECU manufactures but there are many questions your should ask yourself when selecting an ECU for your particular application and here some of them:
How many ignition and injector outputs does the engine need?
How many aux inputs and output does the engine need?
Is the software user friendly?
Does the ECU require further add ons to run correctly?
Will YOU receive all the support and help you need from the Dealer?
I personally have my own opinions having dealt with almost every popular ECU manufacture as well as installed and tuned so many i dare not to count, but every car is different and so are YOUR requirements as the end user.
TWO examples of incorrectly selecting an ECU are:
1. If you have a Toyota AE86 street car with an Normally Asperated 4AGE engine that you drive every day and you 'heard' Motec was the best ECU you could buy and bought the top of the line M880. But your not using 4 of the ignition outputs, 4 of the injector outputs or 8 of the aux outputs let alone the super advanced onboard Data loging system as used by V8 Supercars.
2. If you have a Nissan R34 GTR race car running E85 and it was making 600hp runing 30psi with a flash tune but the AFM is maxed out, time for a Stand alone ECU. Your mate runs a Microtech in his Rotary that makes 900hp and he loves it so you buy a Microtech but it does not Data log, it only has 16x16 mapping and the mapping only reaches 24 psi.
In Summary you need an ecu that doesnt over perform nor do you want it to under perform, you need to find an ECU that meets your expectations its always good to have an extra output or 2 should you expand sensors or upgrade down the track.