I do not have a Snow Leopard machine here to test, but there should be no problems with the 3800 on SL as long as you make sure the OS installer/updater doesn't overwrite some of the 3800 driver files. This can be done by following Lloyd's workaround (also described in these forums elsewhere).
As far as the 6.5x driver vs 6.11 driver, I don't believe that's an issue. To the best of my knowledge, 6.5x offers no practical advantage over the 6.11 driver for the 3800 model.