Buy for Sweat and Water Resistance
The AirPods Pro are IPX4 rated for sweat and water. This means that they are protected from water splashing in any direction. You definitely won't want to submerge the AirPods Pro or take them swimming, but if you sweat on them or use them in the rain, you should be good to go.
This is the same water resistance as the Powerbeats Pro headphones Apple also makes. If you sweat a lot or run in the rain, snow or fog, this is a good reason to buy the AirPods Pro.