"Best" is a relative term. Best for what?
I had the Xcharger Xtreme on my 2006. Loved it, and it was enough to put my convertible into the mid 12's. With the new option to swap the MP90 blower for a TVS more power can be tapped (the MP90 couldn't produce any more than the Xtreme is capable of).
If you are looking for "best" for low end torque, then the Xcharger.
If you are looking for "best" for top end, then procharger.
If you are looking for "best" for a bragging rights dyno sheet, then as far as superchargers the procharger or vortech will get you bigger dyno sheet numbers than the Xcharger Hi-Po. If you want "best" for looks and sound, then Xcharger.
If you want "best" for power then get a turbo.