Hi Mr Brown, I can offer an opinion here.
I recently auditioned both the B&W 685s and CM1s. I personally found the 685s perhaps a little more open, detailed, clear and 'dry'.
I found the CM1s 'warm' perhaps a little fuzzier but with, for me, a more enjoyable sound overall.
I found the volume/quantity of bass to be reasonable on both- perhaps there was a perception of having more bass on the CM1s because they were 'warmer' and less detailed. I found the 685s had a clearer bass (and clearer sound overall) but for me they were less engaging.
I hope this helps you to choose,
James