Tour Magazine had a test with both those wheels (Jet 9 2011 and 808 Firecrest) last year. I think it's available at Tour's site, but else you should be able to dig it up with a bit of search here on the forum. It's been mentioned and linked to several times.

IIRC 808 beat Jet 9 by 2-4 watts depending on yaw angle, though rotational drag wasn't measured, which could skew the results a bit both ways - probably not by much though, as the wheels/spokes are pretty equal. The test was done with a 23mm Continental tire (GP4000S, I think).

Edit: Luis B beat me to it.