I expect that most of the travelling public have little preference.
Which is an important point. I would suspect that the travelling public would like a train which gets them from A to B as fast as possible, on time, has enough seats for everyone (apart from peaks) and offers decent legroom. Beyond that I doubt they really care if the windows are a bit smaller than Mk3s or if there is some noise from the engines under the floor. In which case for the railway MUs make the most operational sense as they can meet the main requirements that the passengers have and are also the best solution for the TOCs themselves.
But rather than guessing what the public want perhaps someone should ask them what they think?