One big advantage that the Brompton has over any other folder is that it will fit between the seat backs of a standard train carriage. This means that you can jump on the train anywhere and easily store the bike without the need to use bike specific parking areas.
Agreed.
On many trains and buses, there are no bike specific parking areas at all! The OP didn't mention multimode commuting involving a train or bus but this certainly is the area where the Brompton excels.
I posted real pictures of buses in New York City and you can decide for yourself ,what bicycle would you prefer to have during rush hour in both instances.
1. New York City Commuter Bus -- This bus looks wide inside but during rush hour, almost all available space is taken by passengers standing on every available spot. I can just imagine taking a Tikit or Dahon inside this bus at 5:30 PM because a large package like that would take up the entire walking space of the bus. In most cases, the driver will not allow you to board.
The Brompton although would be one of the few that would work although. Even covered, it would only take up about 50% of the walking space. There's also a spot behind the rear seat just before the rear door that it will fit nicely. Trying to lug a large folder inside a commuter bus during rush hour is the main reason I have yet to see any Dahon's or Tikits inside the cabin.
2. Greyhound Bus -- This bus looks very similar to many coaches in Europe and the U.S. I take an express bus like this to work some days and the ONLY place to put a folder is in the overhead rack. There's no rear door where you can place the bike and you can forget about placing it between your legs, middle of the floor or back of the bus.
Believe it or not, the Brompton will fit in that overhead rack! I tried it once and there is someone else who commutes into the city that does this on a regular basis. Although Greyhound will allow you to store the bike underneath the bus, many commuter coaches will not.
The Brompton gives you options the larger folders don't when it comes to especially tight situations. Other than the Brompton, Strida or CarryMe, I would not want to do multi-mode commuting on the bus with another folder.