The SMARTY brings the power on a lot quicker for the low end torque, it flattens the power curve out. On the downside it can actually lower your top HP ratings though. It all depends on what you use your truck for.
I had a borrowed SMARTY for a while stacked with my Drag Comp and the power on this truck was insane in both the high and low end ranges. But I'm a poor man and couldn't afford to buy the SMARTY so I had to send it back. Now I'm tryin to sell the comp so I can get a SMARTY. I need the low end more for pullin heavy trailers, this is a farm truck. The Comp is nothin more then a toy in my world and right now I can't afford toys. If you still have this when mine sells you can consider it sold.