true, but seeing that both handhelds have just about the same ability in terms of tuning, i really dont think it matters much. both have fuel and timing timing in 2 rpm ranges. not much more than that to it, pretty general and easy to use.
besides, if youre going to a dyno, the info you want is from the wideband o2. do a run, see where your rich/lean, and make some changes via the handheld, and run again. first and foremost on a FI or NA app, get timing advanced as much as possible, thatll net more power. then if you have timing as far as itll go before pulling timing(which will show as a bog in rpm increase, as it should be a gradual line or a fast spike, if it starts to slow down, you have issues), you can either add fuel if you can to help ward off preignition/knock which will get timing back on track but run richer up top, or you can back off the timing and get the a/f into spec. its all personal reference. for nitrous
fed apps, you want very little timing. i think the given is every 50shot is a reduction of 1* of timing, though im not 100% sure on that. with nitrous, having low timing and a correct a/f ratio is the key issue at hand. a good a/f to shoot for on nitrous is richer than the a/f for a fi/na app, people i know usually shoot for a 10-11:1 a/f ratio. on fi/na apps, as close to 12:1 is pferred depending on setup(how strong the motor and power/heat it can handle, as you get closer to stoich at wot it builds up more heat exponentially)
tuning a car is really not as hard as its made out to be. i really wish there was a program im used to in the dsm world on mustangs, it would put all these tuning companies to shame in seconds, and using it is worlds faster than any handheld that takes 5 minutes to upload a new tune/prefrences into the ecu, whereas i was used to clicking "copy to ecu" and it was done in a second, and could even be programmed WHILE car was moving, making changes didnt affect the ecu at all, i could be doing 3rd gear pulls while my buddy was holding the laptop, and id be telling him what to change.