There was a horrendous hinge defect with 2008 Dahons, they didn't clamp properly at all. The bikes were junk.
The Brompton hinge was designed with wide manufacturing tolerances in mind (as with nearly all things Brompton); they opted for a concave plate that alleviates the need for precision-machining as they only touch on the outer edges (the result is that they act as springs and flex). With Dahon you get CNC machined hinge plates that are supposed to fully buttress against each other resulting in much more stiffness so long as the latch is correctly adjusted. With that much greater surface area contact you get more friction if those surfaces should fractionally slide against each other, hence the tendencies of Dahons to creak somewhat once the powdercoat abrades and aluminium rubs on aluminium.

On the Tern forum there are reports of creaking so it seems they haven't eliminated it entirely. But if you want stiffness the Brompton hinge design won't do.