Lourenz- I understand how they work, I've had both in my system, have you? Both units are being purchased by audiophiles as jitter reduction devises, and as such when connected between the same transport and dac, my experience was the DL improved the sound, while the BB degraded it. The set-up performed at 44.1 was transport AES out-> BB AES in-> BB AES out-> dac AES in. There are many BB users using the unit in this manner, and they feel it makes an improvement.
I agree that clock slaving a transport to a DAC should produce an improvement, but most consumer transports and and dacs(including mine) do not have word clock inputs/outputs, so few will be able to use the BB for this function. I haven't tested a BB in this manner, so I don't know if it reduces jitter and improves performance.