it depends what has been done to the motor, mods etc. also what you want out of the motor, cruiser, performance, etc... i got the haltech F9 only cause it came with the car and is completely stock at the moment but when i do all the mods im gona go for a full management setup.
also with the haltech there are alot of variables that you can adjsut to perfect the motor but at the end of the day it is only limited to fuel, so everything else is done manually, ie, if you change timing, injectors and what not it needs to be re-dynod but with full management you get the hand controller which allows you to do it without the dyno (but of course nothing is better than the dyno)