Ahh...let's breathe some new life into this great thread. :)
I just saw a P50 next to a 503 and thought the 503 was brighter and had a bit more punch. To me, the Fuji...er, FujiTSU...was more panny-like in it's pq, e.g., very dark blacks with some loss in shadow detail and more subdued (natural) colors. I guess this makes sense in part given they use the same glass.
I really want to see an Hitachi HT55 panel since the cmp4202 was really good IMO. Unfortunately the commerical Hitachi (CMP 5000) is a re-badged 503 and I'm not sure what that will mean going forward as it pertains to the cards.
Oh...and I agree with that earlier post that said the river scene was greener on the Fujitsu. I know you need to take the pics with a grain of salt, but I just thought it was ironic that it wasn't the pio that had the greener slant given all the press about it's tendency toward green.