i don't own either one, but i got the chance to get a really good look at both of them and if they were both free sitting in my driveway and a guy said pick one you have three seconds, i'd grab the CET in one second's worth of contemplation.
think of the CET as a ford f150, and the fb500 as a mercedes. the fb was very beautifully designed, like NASA made a printer very nice. but it was very compact.
on the other hand, you open up the hood on the CET there is ample room for diagnosing issues, it's laid in a very obvious way. the printer's visibility is great. ...no "hidden printing going on". also, the CET look literally military issue. and best of all they guys at CET were amped about being a part of CET. in the HP booth, well here's the printer.... "next".
plus chipped ink! argh! for the $100,000 a customer spends HP still believes that they deserve all the ink sales as well. in flatbed printing there will eventually be a specialized product, and that product will require a foreign ink.
i also liked the frankness of the guys at CET. they admit that flatbed/hybrids still aren't as mature of a technology as they could be amongst all manufacturers. and encouraged the idea of getting on the phone as soon as something quirky came up.
in the end i decided to build a massive flatbed for my processes. looking forward to getting the table in over the next month (7' x 24'!!!!) but if i had to put down the money it would have been CET all the way.