Flask is great. Off the top of my head, Falcon's smaller dependency list is nice if you're managing server environments. Flask currently depends on Werkzeug, Jinja2, itsdangerous, and markupsafe, as opposed to just six and mimeparse for Falcon.
That is a nice competitive advantage over Flask, but Bottle has no dependencies whatsoever. And besides a slight performance advantage over Bottle, I don't see any significant reason for me to switch to Falcon.
