A supercharger is not necessarily more reliabe. I know people who have had problems with belts breaking, and with internal bearing failure. As for turbos, look at AA's turbos, they are very reliable and have been proven. If you don't believe me talk to ///MCubed or Blown M Compact(Lou) or TampaTurboM3(Tommy) or Shingo, these guys will tell you. The only things they have problems with are driveshafts breaking do to the amount of power being produced. Another thing I don't like about the supercharger is the problem with heat soak. ///MCubed, Blown, and Shingo all switched from s/c's to turbos. How many people do you know have switched from turbos to s/c?
Look here, the above named guys provided great insight on the subject and about their turbos in comparison to their s/cs.
http://activeautowerke.com/turbo/cus...al_M3_STG2.asp