In my opinion these companies are both unstable, with top level management in each distracted by trying to destroy the other. If I bought a bike from either I would be worried about quality control and about availability of parts down the line if one or both go out of existence. If I had to choose one, I'd buy Dahon, because they are a big seller of folding bikes (world's biggest, I think) and have been around for a while, while Tern is far from established, has yet to deliver a bike and was born into this conflict.