I've had the opportunity to use both.
I've used a 4B-SST(for about three years) and now use a McIntosh MC352 in my main system.
Both are well made, excellent sounding amps. However,the Bryston presents a much different sonic picture than the McIntosh. Without dissing the Bryston, (unlike some in this thread do to McIntosh), I would have to say it has a brighter,perhaps even an etched quality,especially in the treble region. The McIntosh is way more neutral sounding,Is it softer, rounder?...yes, but not dull in any way. I'd say more musical and far more listenable than the Bryston.