Which is better for hard floors?

The Xiaomi S20. It mops as well as vacuums, and its laser mapping covers rooms more systematically. The Shark R75 is dry-only and aimed at carpet.

Which lasts longer on one charge?

The Xiaomi S20, at up to 120 minutes versus about 60 minutes for the Shark R75. The Shark charges faster, in about an hour.

Is the Xiaomi worth stepping up to over the Shark?

Yes if you want mopping, mapping and longer runtime. The Shark is the simpler choice if you only need dry carpet cleaning.

Which is better for carpets?

The Shark R75 is built around carpet upkeep and has a low profile. The Xiaomi still handles low-pile carpet and adds mopping for hard floors.

Which works with voice assistants?

Both work with Google Assistant. Only the Shark R75 also supports Amazon Alexa.

The Xiaomi S20 at 60 dB, slightly quieter than the Shark R75 at 62 dB. Neither is silent.

Xiaomi Robot Vacuum S20 vs Shark ION Robot Vacuum R75

Buy the Xiaomi S20 if you want one robot that vacuums and mops, maps your rooms with laser navigation, and runs about twice as long per charge. The Shark ION R75 is a simpler dry-only vacuum that suits carpeted homes and people who want a quick, low-effort clean. The Xiaomi wins on features and runtime; the Shark is the more basic machine. Owners of the S20 like the app maps and mopping; R75 owners report it handles everyday carpet debris but needs help with navigation and has no mop.

Choose the Xiaomi Robot Vacuum S20 if you have hard floors and low-pile carpet and want vacuuming plus mopping with laser mapping and app control.
Choose the Shark ION R75 if your home is mostly carpet and you want a straightforward dry vacuum with Alexa and Google voice control.

Prices

Shark ION Robot Vacuum R75: $21.00 at Whatnot (checked today)