I preferred the Revels over the 800s when I auditioned them in a dealer's showroom. As usual, direct comparison was somewhat hindered by the differing placements of the two subjects but there was no mistaking the extra brightness (sparkle if you're a B&W fan) of the B&Ws. It was exciting, big and wide, but an artifact that seemed to be present on everything we played.
I'd assume the B&W's higher sensitivity is of benefit in studio work but I think the Revels have a more balanced sound with smoother mids and highs.
John Atkinson's measurements suggest to me that it should be just the opposite (the B&Ws should sound darker?) but I didn't hear it that way.