Even among coaches, there is often confusion about the merits of steps vs. chassés. Sometimes a coach will teach only chassés, believing that they make steps redundant (this is an error).
The reality is that both steps and chassés are useful, but they have different merits.
Steps: the fastest way to cover distance
Consider (again) a 100m race. If one of the runners decided to use chassé steps instead, how well do you think he would perform?
Chassés are much slower at covering long distances, because the length of each stride is smaller. Because of this, there are many situations in badminton where running steps are by far the faster method to reach the shuttlecock, and using a chassé instead would just be silly.
You should generally avoid stringing multiple chassés together for covering distance. Running steps would be faster. Most of the time, it’s inefficient to string two chassés together; and you should certainly not string three chassés together!
(This is not the same as following one chassé with another. Multiple consecutive chassés can often be useful to help you change direction quickly.)
Chassés: dynamic footwork
Chassés, although slower over distance, have some interesting advantages over steps.
Chassés are adaptable for different distances
The effective length of a running step is fixed by your leg length: short steps are a hideously inefficient method of movement. Chassés, however, remain efficient regardless of whether you need a full-length chassé or a small adjustment chassé.
It’s important to realise that you do not need to bring your feet fully together for a chassé. This is optional; sometimes the feet come almost together, and sometimes they stay wide apart. The more distance you intend to cover with a single chassé, the closer your following foot must move to the leading foot.
This is what makes chassés so adaptable: you can speed up a short chassé by moving each foot only a small amount (so the feet don’t move close together). This doesn’t work with ordinary running steps.
Because of these differences, chassés are faster than running steps over very short distances. They also keep you on-balance throughout the whole movement, and minimise body rotation (which can get in the way of hitting a good shot).
Chassés help you jump
Unlike running steps, chassés keep both feet close to the ground at all times. A good chassé feels like you are skimming across the floor! Chassés also keep you in a balanced position at all times, whereas a running step depends on using imbalance to create movement.
These differences make chassés more effective than running steps when you want to launch yourself into a jump at the end. At the end of a chassé movement, you have both feet wide apart and on the ground, and you are well balanced. This helps you to make a powerful two-footed take-off.
Running steps, however, generally force you to use a one-footed take-off if you want to move immediately into a jump. One-footed take-offs are less powerful.