The pro has an M1 chip, while the Air is M2. Which might not matter because the M1 is plenty fast for a tablet.
The pro has lidar, the air does not The pro has better speakers and better microphones The air has the FaceTime camera on the long side, where it belongs They support different pencils (the air supports the new pro pencil and all its features) The air is lighter The pro has 120Hz The pro has an additional wide angle lens, while the main camera of the air is probably a bit better now due to processing. But in the end, who takes pictures with a tablet. The air has better WiFi and Bluetooth. The pro has thunderbolt and everything, while the air only has normal usb-c.
Pick what is important to you. Keep in mind that the battery of a 2 year old device might not be in perfect condition.
Personally, i think the differences are negligible. I would go with the cheaper option