Folding bikes vary quite a lot in performance. If getting close to the speed of a road bike was a priority for you then select a folder that has fast rolling rubber, reasonable weight and a riding position that is reasonably aero while allowing you to develop power efficiently.
+1
You can buy a BF Pocket Rocket Pro with full dura ace components (or campy, too) and it will be under 20 lbs and ride just like a light road bike. Which may or may not be the best choice for commuting, but YMMV (literally!).
