I did some research and found out that the S6 Pure has
- has two less "drop sensors" (which doesn't seem to limit it in any way)
- comes with fewer accessories (but only the wet cleaning cloths)
- has a simpler docking station (without integrated cable management)
- the parking plate on the docking station is thinner and for sticking on the floor (S6 has a more solid plate for sticking on).
In terms of suction / mopping performance, the S6 and S6 Pure are obviously completely identical.