The FX9 offers 6mp in the same camera and same sensor size as the FX8 (5mp). The FX9 is a lot more noisy and loses detail because of noise reduction procedures, and therefore I always say the FX8 is the better choice, all of the plusses of the FX9 (compact, stylish, image stabilized) without its minusses (lesser image quality, more noise).
The FX8's sensor is just the better sensor, it is just that megapixels sell (they do not necessarily give better results).
Here you can see the difference:
Full size photo from Jeff Keller's review of the FX7 (FX8 is an updated FX7):
http://www.dcresource.com/reviews/pa...w/P1000029.JPG
Full size photo from Jeff Keller's review of the FX9:
http://www.dcresource.com/reviews/pa...w/P1000099.JPG
You will notice that in sharpness, CA, colours, the FX8 is better.. it just is the better camera (and in all a very nice compact camera).