I have APR, but if i had the choice between those two, I would go with REVO. Nothing against GIAC, they have some freaking sweet products with VF Engineering, but the ability to fine tune with REVO sounds awesome. Be ready to run logs though. The last thing you would want to do is set your fuel, boost and timing in some fogged up way that will screw up your car. Dont know because I dont have it, but play with it and run logs to see what the hell you actually changed.