Originally Posted by bigrog
And that's the main reason why I joined, I am interested in finding out why?
Mostly because we're a bunch of crotchety old bigots who are set in our ways.
Actually, there's not one single answer.
Probably the largest contributing factor is political. Historically speaking, those companies which are best-known within the MX5 aftermarket for supplying turbocharger systems have gained strong positive reputations for being run by people who are technically competent, well-versed in engineering, electronics, engine management, mettalurgy, etc., and are just generally good people to work with.
By comparison, the supercharger market within the MX5 community has tended to be populated by bullshit artists who outsource all of their engine-management design, don't have an especially good understanding of the product that they are selling, over-hype their claims (and, in some cases, lie outright), and are in general just better at marketing than engineering.
As a result, supercharging, as a general concept, has picked up some of that slimy reputation.
Then, there is some technical justification as well. Superchargers, especially positive-displacement blowers, do have a performance edge in drag racing owing to their instantaneous off-the-line power delivery. Of course, drag racing isn't really acknowledged as a legitimate motorsport by most of the MX5 community, partly because we're elitist ******** and partly because our cars aren't very good at it. We tend to look at the efficiency and performance of forced induction systems across a rather broader range, and here, the greatly increased efficiency of an exhaust-driven turbocharger places it well ahead of a comparable supercharger system in terms of HP-per-dollar, torque-per-BMEP, and so on.
There's a lot more that can be written, but that's basically the short version. Turbochargers are slightly more efficient than superchargers (more power per dollar spent), and the companies which have historically sold supercharger systems to the MX5 community (especially those based on the Eaton M45 / MP62) have tended to be kind of sleazy to deal with.