I am not currently running WI/AI (so others will far more experience than I may disagree), but I would think you would get a lot more flexibility out of WI with engine management. Flexibility such as: low boost failover if you get a plugged line, pump failure, etc. (assuming you were running something like an Aquamist 2d WI setup).
You would also get much more power by being able to advance timing, etc.
I would think that the shortcomings of boost controllers with pump gas would only be amplified by moving to higher PSI with WI/AI.
Also, while the Knock Sensor is useful in tuning, it's more of a safety feature, and isn't a substitute for a wideband O2 or EGT gauge in tuning, I would think. As I said, I am not that experienced in this area, but I would think you would have a much more solid setup (safer, more power), if you spent the $650 on EcuTek (or Utec, Xcede, etc.) and a few hundred dollars on dyno tuning by a tuner with WI/AI experience.