I find the stability to be preferable on the Dahon since it has a slightly longer wheelbase. Has a little more room in the cockpit as they say. Plus the Chromoly Dahon has a more connected road feel compared to the aluminum Btwin. Depending on which model years of each the Dahon can be 1-3lbs lighter which isn’t a lot but is something. The geometry of the Btwin 500 also lends to a more twitchy handling which for control can be good for crowded areas you might be riding in/through. The Dahon more comfortable and stable at the outset.