This thread is going to start a war!
Okay, let's be honest here, since this thread was started in the Salk Forum I think we all know which speaker will be preferred. With that said, I'll happily answer your question.
I'd hands down choose the SoundScape 8 because it outperforms the B&W in every way to my ears. The bass is tighter with more punch (perhaps a lower woofer Q?), the midrange is more defined and detailed and doesn't beam off-axis like the 802D does, and the tweeter on the 802D is just too bright for my ears. In comparison, the RAAL ribbon is more accurate sounding, with better timbre and tone reproduction without losing detail. Each instrument - even brands of instruments - have a certain pitch and tone, and that along with the harmonics is what gives it its unique sound (if I understand that correctly), so reproducing the proper tone/timbre is extremely important in order to portray each instrument as what it is. You wouldn't want a flute to sound like a wood instrument, right? I feel the SoundScape 8 does a much better job at telling the listening exactly which instruments are playing, provided they are familiar with what those instruments should sound like, of course. I hope that makes sense.
One other obvious difference between the two speakers: price and customization. I know you said "at the same price," but they don't cost the same, unless you're getting a good discount from a dealer. So let's say they are the same price and turn our focus to customization. You cannot fully customize the aesthetics of the 802D, but you can with the SS8. You want Ferrari red paint and high gloss with white racing stripes? Cool - you pay for it and you'll get it. You want a design stenciled on the inside of each speaker? Sure, Salk can do that. And it'll still cost less than the 802D.
Hope that helps.