Apple updated the iPad Pro in March 2020 and the iPad Air was updated in September 2020. The iPad Air has a slightly newer 5nm A14 Bionic chip whereas the iPad Pro uses the 7nm A12Z Bionic chip. Both the devices are powerful and are almost very similar in terms of design.
The iPad Air is cheaper compared to the iPad Pro, retailing at just $599. The iPad Pro on the other hand retails for $799 for the base model. The base model of the iPad Air packs just 64GB of storage whereas the base model of the iPad Pro packs 128GB of onboard storage.

Authentication method and display
The iPad Air has a TouchID sensor built into the power button which allows users to unlock their iPad Air with their fingerprint. The fingerprint reader can also be used for authenticating payments and apps which support logging in through TouchID. On the other hand, the iPad Pro uses FaceID for authentication purposes. Using FaceID is much easier than TouchID, as the sensor on the iPad Air is not upto the mark.

TouchID is supposed to be much more convenient in some cases, especially when wearing masks but people usually use their iPads at home. On the iPhone, it makes more sense to have a fingerprint reader as the device will be used on the go. However, the facial recognition technology is far more appropriate on the iPad (Pro). It would be nice if Apple brings FaceID to the iPad Air in the future.
The other major noticeable difference between the iPad Pro and the iPad Air has to be the display. The iPad Air uses a standard 60Hz refresh rate LCD display whereas the iPad Pro uses a 120Hz high-refresh rate LCD display.
The iPad Pro is a much better package with 120Hz display and 128GB storage for the base model. However, if under a budget, the iPad Air does the job as well.