The sc12 has no power in the top end but the sc14 does, depends on what supercharger and how its setup, you can't just say all superchargers run out of power in the top end as its just not true.
I doint know about the teflone coating coming off at 13psi unless the sc14 was really flogged out, i know of sc14s running at 17psi daily without a problem....
Sounds like a cetrifical (think thats what there called) supercharger, basically the rear housing of a turbo with a pulley mated to the front, also sound like he needs to tension the belt, had that problem before,
Depend what you want from your car mate, power from idle and wikid supercharger wine or do u prefer waiting abit longer for the turbo to spool? either way u will be able to get decent power