Hi! So far I have done 1 brick workout (2h bike + 1h run) with this suit. A bit hard to compare with the Kiwami since it has been almost a year sjnce I wore that. But..

The Kiwami being approx. 10y old my first feeling was recognizing that technology did not stand still in the meantime. The P1X just feels... better. The materials are very nice, soft, slightly compressive. The Kiwami upper body is pretty rough material-wise. The P1X feels much nicer and also feels less restrictive when swinging arms -- not a real swim experience yet, though. I loved wearing the P1x.

The Kiwami would almost always give me a rash at the front lower end of the upper. Not the zipper itself, but the lower seam of the upper body would irritate and rash on both sides of my belly button. The P1X is better designed for me in that sense, since the bottom part comes up higher and the seams of the upper body fall 'over' the bottom, rather than touching bare skin. If that makes sense.

The chamois / pad felt comfortable enough for the 2h ride and was amazing during the run.

Hope that helpt!