Nitrous would probably be the safest if I had to pick one.

And ive had 1 turbo car, and currently own 2 supercharged vehicles, so dont think im being biased lol.

All 3 are safe though. All 3 can destroy your motor.

1993 SVT Cobra, Vortech blown, 11.1@133MPH Street Driven 2000 SVT Lightning 1998 SVT Contour