turbochargers & superchargers for the gts cost around the same (4k-5k--not cheap).
all Turbochargers have a bit of a lag while superchargers work immediately.
turbochargers can usually push more whp and torque than a supercharger does.
superchargers are, as a rule of thumb, more reliable.
imo, i'd go supercharged..but blitz still hasnt released there's i don't think. the xs Turbo has some problems and the strafford Turbo seems promising as well as a grand or 2 cheaper