If coolest mean most versatile, for me the Birdy is the best:
- Rides very efficiently (with derailleur or Rohloff) due to rigid frame, efficient transmission, efficient full suspension, wide tires.
- Rides also on unpaved roads/trails.
- Very comfortable.
- Adjustable position on the bike due to height and reach adjustable stem, adjustable seatpost setback, two different stems (sport and comfort).
- Folds not as small as the 16" Brompton but very small.
- Offer the best possibility to carry things: rear folding rack for big side pannier, front rack for low rider, Brompton block adapter fro Brompton front bag.