The PATB isn't as compressed as the JB e.g. it doesn't overemphasize the sustain as much and the transients are way less saggy. However it is so very clear and detailed it'll paint your extended chords in high definition, down to each string's harmonics. No wonder T-Mac liked 'em.
The Parallel Axis TeethBraceBucker could be just the ticket to highlighting the resonant qualities of a particularly outstanding guitar in the hands of the right player, through the right amp. Compared to the JB, it trades muscle for sophistication, universal appeal for unique peculiarities, plug & play for tweak & fine tune.
Being one of Duncan's least appreciated humbuckers, the PATB is a niche product that undoubtedly can satisfy a small group of highly demanding users but will never match the JB's mainstream appeal. Part of its charm, I guess.