If you do a search on the boards, your bound to find many MANY threads on this very topic. In my opinion and to my knowledge it all really boils down to the following:
-Centrifuge SCers (Vortech, Paxton, etc.): Build HP with RPM's making excellent higher RPM HP and great for on the track.
-Roots (GT500)/Twin Screw (Whipple, Kenny Bell): Almost instant torque, most of it by 2k RPMs; great for a daily drives/"big block" power out of small block engine.
-Turbo: best of both worlds?
In the end it was simple for me. I was originally going with a Paxton from Shelby, but once the Whipple became available I knew I wanted it. Since researching the topic for years, I figured a roots/twin screw suited my needs (near daily driver - not much track time and certainly not a serious racer) perfectly. Just my 0.02.
Thats a great question and I'll be meeting with my insurance agent in the next few weeks to discuss this very topic. Being it winter she doesn't see many miles of road way so I held off a bit on any "extra" coverage until it gets nicer out. I did however pick up new car replacement the day I bought the car. My agent told me that whatever I paid in total for the car (total price including trade, money down, etc.) would be included in the plan...on the cheap too!