The Mu 24sp and BF are both excellent bikes. There are some customers who have had issues with the tikit's frame cracking, that was quickly addressed by BF. There are some cases of customers who experienced problems with the Dahon, but there are lots of happy one too, more so I would bet.
I think the Dahon frame requires more regular checking than the BF to keep it tip top and it helps a lot if the owner is aware of this and knows how to keep things in top condition.
My own subjective opinion is the BF frames are designed better (not because it's in the US!), but I am more than happy that most of our bikes have frames built in Asia (Pacific Cycles for two of them). Those welds are just perfect. Give me a mass-produced robot weld any day. As far as I am aware I have never seen any report of a frame failing because of a dodgy weld. It's usually a crack in a frame tube at a stress point.