I looked at the Brompptons but just couldn’t reconcile the price and the weight. They also didn’t ride at all well.
I’ve now got 2 folders – one’s a Trek-badged Dahon, the other a proper Dahon. The Trek was secondhand (£200) off the classifieds, and the other one is a Mu SL, which really is a cracker. Very quick, and quite a lot of fun.
Both fold small (though not as small as a Brompton) and are fine for putting in the car or taking on a train. If I were a regular bus-traveller then I’d get a Brompton – they really do pack that bit smaller. But they ride a lot worse, IMO; much preferred the Dahon’s slightly more bike-like feel.