If I had to buy one of those projectors myself, I would get the Sanyo as the only viewing I do with front projectors is upconverted DVD and HD material. The sharpness level of the Sanyo is noticably better and I like the added lens shift which would allow me to flush mount it against my 9 foot ceiling.
But, the Panasonic is a bit brighter, which is noticable, and the image, while noticably softer, definitely has it's advantages in close seating arrangements. HD material on the Panny is spectacular, just not QUITE what it is on the Z4 at a proper viewing distance. Yet, when you get closer, the AE900 retains its smooth image while the Z4 will start to show visible pixel structure.
No, neither is a 'clear' winner IMO, but both are excellent and it more is a matter of how the room will be setup. A dedicated theater from appropriate viewing distances with high quality sources = Z4 while a more versatile rec room which may not have 100% light control always and seating may not always be optimal = AE900.
They are both great though.