I got to run the BO6040 at a local detail shop here recently and it is definitely a nice smooth running machine that seems to cut defects considerably faster than the 3401 (I own two 3401s) If I had to choose between what I know about the 3401 which is that it's an unstoppable, very high quality machine that is very reliable and just works period, and what I experienced within a few minutes of trial with the BO6040 I'd stick with my 3401.
What worries me about the BO6040 it the switchable function that goes between regular DA and forced rotation. When this detailer switched it over it seemed like it was broken in one mode as it made some grinding noise and didn't seem to be orbiting properly on the paint.
I'll pass on the gadgety switchable machines. More moving parts = more troubles as far as I'm concerned.