Xcal all the way with custom tunes. See the ones from a store just have default tunes. They have no idea what is already on the truck prior to programming. With a custom tune you actually talk to the guy who is making the tunes for that programmer and tell him whats on the truck to begin with, any mods, diff tire size etc. Got mine a few weeks back, and wow what a difference it makes especially in towing and shift points. The Xcal lets you do all kinds of stuff too, rev limit, idle speed, diagnostic stuff, etc. It's sweet and I highly recommend!
-2011 F-150 Lariat: 5.0 "Coyote" V8, 6-spd Auto (6R80E), 3.73 ELocker. White Platinum Metallic Tri-coat.
-1992 Ford Ranger: 4.0L OHV, 5spd (M5OD-R1), 3.27 Open.