Originally Posted by pm124
As far as hinges go, it depends on the bike. The Birdy, Swift, Go Bike, and Bike Friday have no hinges. Now, the range of hinge-free bikes is so large that you can get a true small space performance folder (e.g. Birdy), a fairly cheap closet/car bike (Swift)
Don't forget the Carryme. It also have an unsplit frame and is the perfect bus companion. Noticeably less flexy than my Downtube. In fact, since most of the flex on my Downtube seems to be in the handle bar stem, I imagine the Carryme is less flexy than the split stem Birdy too.