In my honest opinion , from what i have heard and witnessed firsthand , SCT is a much better product than Diablo. Our authorized Diablo dealer on the island cant even get close to the numbers i get tunning my 00 vortec gt with the SCT Pro racer package, and i am by no means an expert or tuner. Most of my friends with Predators ended up switching to SCT Xcals , the numbers dont lie.