My Bike Friday is my normal commuter, but maybe one day in 10 I'll take my 3 spd Brompton in. There's normally not too much difference on my 17 mile RT commute (maybe 5 minutes), although if it's windy (as it has been here a lot), the additional gears on the Friday are useful. But if I'm planning on running errands at lunch while I'm downtown, the Brompton is a little more convenient since I can fold it and take it inside places if I want.