I have experience with both amps but there has been five years between the two sessions so direct comparisons are not possible. I liked them both and found them both at the time very musical and accurate. Like Mike, I would like to own a P1 sometime in the near future.
How about hopping a flight to LA on May 29th for CanJam then you can audition them both with your own cans? For such an important decision as this, a mere plane ticket is worth the experience almost as much as the postage and insurance back and forth on an amp you choose to return. Perhaps you may even discover something else that will strike your fancy.