LiDAR vs gyroscopic navigation is the difference between a vacuum that knows your room and one that guesses

Between the two Xiaomi models, the navigation gap is wide enough that it should probably be your deciding factor. The S40 Pro uses LiDAR navigation — the same tech you see in higher-end Roborock and Dreame models — which means it creates a real-time map of your space, knows exactly where it is within that map, and plans efficient cleaning paths without bouncing off furniture. The H40 relies on gyroscopic sensors, which is basically a step above random bounce: it can tell it’s turned, but it has no real idea where it is in relation to the room. It bumps into things and eventually covers the floor, but it takes longer and you’ll hear it bumping. If your floor plan has any complexity at all — multiple rooms, narrow doorways, furniture with legs — the S40 Pro is worth the upgrade for the LiDAR alone.