Re: ...new MIM Jags/JMs!!!
Jazzmaster pickups are more like mellowed-out Strat pickups than P90's. To me, P90's sound ballsy and rude, and are tonally closer to a humbucker.
Really, the only similarity they have is the bobbin shape (roughly - a JM bobbin is larger). Jazzmaster pickups have six pole piece magnets like a Strat or Tele pickup. P90's have adjustable screw pole pieces that run between two bar magnets.