Porsche 911Turbos are expensive and can be tens of thousands higher in price than a normally aspirated 911. They also tend to have more maintenance needs. Turbos also have a, well, turbo look that is not very stealthy, and not for everyone.
Supercharger kits can be had for $15k with gains of over 100HP, and more HP with headers and exhaust. Home mechanics can install supercharger kits over a weekend or two as you are working mostly on the top and front of the engine.
Unlike a turbocharged engine that can peak late in the rpm curve, superchargers provide a nice linear power delivery that builds steadily with engine speed. They also have quick throttle response as boost is always available making the engine feel bigger. The best part is your car remains looking stock and becomes a performance ‘sleeper’.