1) Smart Wheel introduces a brand new electric motor that is thinner and lighter (and more efficient) than any other before it. Copenhagen Wheel uses regular rotary motor that's heavy and cumbersome, not to mention it's not a replaceable wheel - it comes together with the whole bicycle.
2) The GPS module might seems like the only thing that separates the Smart Wheel from the Copenhagen Wheel (it's not) but it's the difference of how they use this data that makes all the difference. Smart Wheel uses GPS data to learn about your cycling habits and routines and then suggests on how to improve them. This data can also be used to help improving the cycling experiences of other people. Copenhagen Wheel measures noise and air pollution levels and uses them for statistical purposes only.
3) Smart Wheel is opensource which means our users will be available to develop their own apps and other tools to find new innovations to using the Smart Wheel. We're already working closely with Pebble Watch and other similar devices are in the works, too.
4) Last but not least, despite being around for ~5 years, Copenhagen Wheel is still only a prototype with no sign of ever being available to the market. Smart Wheel is becoming available in May 2014.