The CS200cad has all the same features as the CS200 plus a cadence sensor, which helps you assess your technique and efficiency when cycling.
It also measures current, average and maximum speed. You can use the combination of data to predict and measure your calorie burn when cycling, using the polarpersonaltrainer.com website as your training log to analyze your long term progression and improvement
See Full Functions & Specifications for the Polar CS200cad