I vote for the Smarty. It will be untraceable.
If you don't get a Smarty, the BDDL will be a good option. It allows you to control a lot of extra functions on the '06 trucks, not just horsepower.
On edit:
Read about the PPE box on DTR (or maybe it was here). Someone had a problem getting their truck re-flashed after returning their truck to stock from a PPE downloader. It loaded some Brazilian tune into the ECM, and a DC tech was not able to updated it. In the end the guy had to buy a new ecm.