This is an extract from comment by a KL rider who owns 2 Brompton bikes and a Dahon Curl bike.
"I have both bike. Both are good in their own way.
Brompton still fold better/smoother then Curl. You can feel the thoughtfulness on how each step it fold and lock to each other. Where else, Curl still have much to learn. There are places you need extra care as not to scratch the frame.
Brompton lock the folk on the rear triangle and Curl lock it on the rear derailleur hanger. I see it as a weak point on Curl that it might break the rear derailleur hanger when transported in as check in luggage. So extra care have to be given to this area.
Built quality on both bikes are very good. Brompton use brazing technique to put the frame together and it is wonderfully braze together. My Brompton raw lacquer are one marvelous piece of art of brazing. It is hand brazen, not by machine.
Where else Curl are using machinery to weld the aluminum frame together. Not much hype on it but it does it very smoothly on every joint.
Now, let’s talk about handling. I’m very surprised how Curl handling is. Very smooth and it absorbs most rough surface very well despite it doesn’t have a suspension block like Brompton. Although Curl uses aluminum rather then steel but I still find it more comfortable on Curl than a Brompton.
Curl cockpit area are bigger than Brompton. That means my knee on Curl are further away from the handlebar than a Brompton. Your body will bend more on curl than a Brompton.
On gearing wise, Curl uses a standard rear of 135mm and you fit in any internal hub you like. Where else, Brompton only able to use Sturney Archer hub. It’s 6 speed 2X3 are slightly complicated and need some time to getting used to but eventually it works quite well after a while. Although you will always feel the ratio is too wide apart.
As we know Curl are new in the market, you will get less people, less hype then a Brompton.
Brompton have tons of accessories on bags and upgrades then in Curl.
It really depends on what you want from your bike. "