This is an interesting question. It all depends on your needs and wishes. The 6008 AF remains a very capable camera.
The main differences between 6008 AF and Hy6 are:
- lighter and smaller
- a different battery (a stock lithium battery instead of proprietary NiCad)
- the motor has been removed from the body (not needed with digital backs anyway)
- autofocus with improved sensitivity, including infrared beam
- handgrip with LCD display forms an integral part of the camera and is no longer removable
- better integration with digital backs (integrated RGB sensor for improved white balance; EXIF data; ability to use AFD lenses in addition to AF).
Do these different features matter for your use? If your main purpose is digital shooting, I would probably take the Hy6 over the 6008 AF. Your choice of backs will be between Sinar and Leaf. With the 6008 AF, the main choice is PhaseOne.
You may find the information on my webpages useful to make a comparison between the cameras. I myself use the 6008 AF with both film back and PhaseOne P20 (Rollei DB20p).