I know Dahon has its fans and the Speed P8 I tried was decent but honestly, between the family drama and where they're made as well as QC issues they've had, I'd rather own a Brompton. The fold is unbeatable and I didn't find the weight an issue whatsoever but then I'm not interested in humping one around folded, it just needs to take as little space as possible when stored.
The Dahons I tried (Curve SL, Speed Uno, and Speed P8) just felt cheap and I didn't really enjoy the ride. The Brompton on the other hand felt like quality save for the shifters and has a great ride. Again though, it's the price that slows me from making a quick decision. It's a LOT of money for a bike that won't get used much and would be purchased just so I can always have something in the vehicle. For no money, I can just deal with the minor hassle of putting my fullsize bike on the rack or buy a trunk mount rack for my wife's car.
It's just that the Brompton is so damn cool...