Alex:The true contrast ratio is 16000:1
That's for the PDP-508XD.
For the 5080LX they are claiming 20000:1.
I have actually seen both screens next to one another. the 508XD is not Full-HD, while the LX is. While I found the LX a tad sharper on close inspection, I could not tell the two screens apart from my normal viewing distance, even with glasses on.
Since Full-HD will reveal more shortcomings in Standard Definition source material, I chose to buy the PDP-508XD - and it truly is a staggeringly wonderful image.
BTW - Our Planet from BluRay shown on the LX was indisputably excellent, but then that's also a true HD source. At home, I have reserved Full-HD for the projector.