Face shields reduce the exposure to and emission of respiratory droplets considerably. If you can get comfortable that face shields provide adequate protection of the respiratory tract, they offer you the following benefits over a face mask:
They cover your eyes in addition to your mouth and nose; they also cover your face so stop the prospect of a respiratory droplet landing on your face which is then (for want of a better word) smeared into contact with a mucous membrane
They make it much harder for you to touch your face
They offer the potential for decontamination and reuse (although disposable is probably ideal).
They have less chance of prompting the occupational hazards of long-term wearing face masks (painful / damaged ears and nose bridges).
With a bit of thought, you could find a way to drink a cuppa and eat a sandwich with them on (possibly).
Itâ€™s easier to communicate through them because people can see your whole face for expressions and lip reading.