Re: Procharger or Paxton.. 5.0 373s 6MT.. Gotta make decision today!
It's not "lag" in the traditional sense of turbo lag. It's just going to be slower to respond around town and at part throttle because the intake velocity is lower, its volume is so much greater and the step-up is less. That's reality.
The basic P1SC Stage 1 Procharger is still well over 500 wheel hp on mustang dynos, that tend to read closer to reality than dynojets. You can still grow with that head unit but, not as much with the Paxton, probably in the low-mid 600s at the most.
The Paxton is widely documented to support over 700 horsepower but, the stock engine won't live too long behind that and you'll be well served buying a bunch of supporting mods like headers/exhaust, clutch, etc. Going that way, I think you would be better off buying a tuner kit and having it tuned locally. You're just pulling the tongue out pretty far for email tunes at that point, in my humble opinion.