:histeric:...a "stock" Z06 with Procharger....
Seriously though, a dyno tune will always get you slightly more power because they can tweak things for your car, and every one is different.
That being said, I'm incredibly happy with my Stealth tune, as Rick has a lot of time and miles in a V to develop his tune. The V is a lot heavier than most LSx cars, so it needs slightly different things to make it feel right. Also, Rick has written the software for some neat extras, like the ability to add a hidden switch that "neuters" the car for valets or teenagers, a lower rev limiter when the engine is cold, fans running on after the engine is off, etc.
It's a tough call, but I'd say go with Stealth if you want the best all around driveability, and go with the dyno tuner if you want every last bit of power.