On a hydra, you can change tunes on the fly. Tunes get emailed to you and then you download those into the hydra chip which takes about 20 seconds per tune. If you get a tune and it needs some changes, then you let your tuner know and they will just email those changes. The hydra also holds 15 tunes. You can run multiple tunes from different tuners. For example I have Powerstruck tunes, Php tunes and Gearhead tunes and I can change my tunes while I'm driving. Simple and easy to do. I've had a Sct programmer w/ custom tunes, I've also had the rotary knob chip. My hydra I have now is the way to go.
2001 F-250 4X4 SCSB 7.3 Auto X Codes w/ 2" Hanger/Shackle Drop Kit-38R w/Turbomaster,AFE, T500, Regulated Return, 6.0 Tranny Cooler, JWVB, 4"Exhaust, Hydra w/ Gearhead, PHP, and Powerstruck tunes, Powerstruck 180/100's Live Tuned by Powerstruck and then some!