Instead of mulling over a tuner unit I'd suggest picking a custom tuning shop that will work with you and what you want. Have the tuner who writes the tunes suggest the platform they like to work with.
You will have direct input on trans tuning and throttle response. I chose BCB because I can drive to the shop and talk directly with Casey, but there are many others around and several are forum members.
BoostKing is often mentioned. KM