IMHO, a turbo is more efficient, (as it's been proven)
however, compared to a supercharger, they will reduce the life of your engine much faster. your dealing with much more heat. they heat the oil, and typically run hotter inlet temperatures than a supercharger. of course, intercooling and the other types of charge cooling (meth injection, nitrous, etc) can negate this a little. that aside, a supercharger gives you boost via rpm and can save your engine, and still give you sweet power. it's probably a little easier to install, but the cost is the same or more for a supercharger. its all preference, i'm just adding a little .02 cents after reading the first page. sorry to hijack if this argument is over, LOL. good luck with the turbo setup