Swift
BF's are excellent bikes, but from what I can tell aren't quite as stiff. The handlepost and seatpost are both is a lot longer than the Swift, therefore more likely to have some flex. Also, the Swift's tubes are larger and made of aluminum, both of which add to stiffness.
That said,
afaik both are significantly stiffer than the Dahon, and it's likely either one will work fine.