Stephen,
The 800 is an HW upgradeable transport, the G91 is not.

The 800 is a very fine DVD and RBCD player. The G91 is a very good DVD player and pretty good RBCD (but not the best).

With the coming HD formats I would rather put my money on the 800 if I had the means rather than G91+RBCD transport.

There are several here that can argument for/against the performances of the components, but I think my first paragraph is what I would emphasize.

DSP8000SE, DSP7200SEHC, DSP5200SE sides, DSP7200SE rears, 861v8, 210, Sim2 Ultranero 4, Stewart Cinecurve 2.35:1, XEIT CM-5E Anamorphic lens, Dune HD Duo Cinema 8K and Wireworld Platinum 48G HDMI -> UHD722 -> Shunyata Omega Ethernet. Shunyata/Furutech power-cables/filters. SR Master Fuse@861v8. Uptone Etherregen with 10MHz OCXO clock.