My iPad Air 3rd gen screen started malfunctioning, so in January 2022, I bought the iPad 9th gen because I didn't want to part with my Logitech keyboard case.

The first thing I noticed was the screen's reflectiveness. While a matte screen protector helps, it doesn't completely replicate the antireflective screen of the Air 3. The difference is noticeable when the two iPads are side by side but it’s not a lot.

Another issue is that the screen protector isn't as smooth as glass, so you can hear it when swiping in a quiet room. However, since I mostly use my Logitech keyboard with a trackpad, I rarely touch the screen. It's not a major issue, but worth mentioning. There might be better screen protectors available.

Performance-wise, I did not notice any significant differences for my daily activities. However, my iPad has recently started slowing down and freezing when watching videos and using Safari after about 2.5 years. Backing up and restoring it has helped. Maybe you could try it, and see if it helps, if you haven’t already.

I chose the 9th gen primarily because it fits my existing case perfectly and has performed well for browsing and watching movies for over two years.

I would recommend the 9th gen as it will get longer OS updates compared to the iPad Air 3 and you can use your existing stand. But you might have to replace both in 2-3 years.