Roots blowers like the KB make power instantly for serious off the line grunt.  Centrifugal blowers make power around 3,000 rpm so are better for a daily driver as you have to get on the accelerator to make power.  So it is really up to what type of driving you like.  No Powerdyne for you though.

Any supercharger will be good.  If I had a Gt I would probably have the biggest blower that KB makes.  Nothing like instant torque.

If considering centrifugal type blowers, a vortech is what you want for reliability.  Prochargers make more power and usually come intercooled, but they are notorious leakers and require more maintenance (Ie: the oiling system)  A vortech feeds off of the cars oiling system, and it constantly cycles through the blower.  a procharger is self contained, and will require oil changes regularly when yo change your car oil.  .A roots or twin screw blower is the ultimate setup....instant power and tq. (no lag) and very reliable....they just cost alot!

My recommendation, for reliability, good power and reasonable price...a vortech v2 sq.