Exactly what I say whenever this question comes up. The tune (in the case of a custom or dyno tune) is only as good as the person writing it. The flash tuner is only the means used to download it, and both the XCal 2 and the Predator are easily used to do so. Some have said the customer service from Diablo is bad; I personally have not had to ask for customer service directly from Diablo because their flash tuner doesn't really require much in way of instruction to use. I have dealt with an independent Diablo CMR dealer in developing a custom tune for my vehicle, and his customer service couldn't be any better. The only times a Xcal 2 would be considered a "better" flash tuner (in my opinion) is if one is going to spend the extra $$ and get SCT's Pro Racer Package along with it and self-tune their own vehicle, or if your favorite dyno shop only uses SCT software.