I was at my local Apple Store yesterday monkeying around with the iPads. I've been considering an upgrade from my 2017 Pro, and other than knowing I don't want another Pro (impossible for me to justify the pricing for how I use iPads), I've been stuck considering Air 5 versus iPad 10.
The joy of the Apple Store was being able to work with both, right next to one another. And honestly, the 10 is really a very nice device. If it were a little cheaper, it would be the absolute value king of iPads because it's better in every way than a 9th gen.
Similarities: The slight differences in weight and thickness are imperceptible. I personally couldn't tell the difference. Build quality is 100% equal. Both feel identically fast and performant despite the difference in processors. Any difference in screen quality (P3 color versus RGB color) is imperceptible, and I'm a graphic designer so I have a particular sensitivity to color reproduction. Reflective coating versus no reflecting coating did not make some huge difference. They're both sheets of shiny glass and both were reflection magnets under the Apple Store's bright overhead lighting.
Differences: Laminated versus un-laminated screen is instantly noticeable, although not some huge deal. If you're used to a laminated screen, the difference is more apparent. If you've never used one, you wouldn't know what you're missing. 4GB versus 8GB of memory is noticeable, although dependent on how you use your iPad. With both iPads next to one another, I started loading up tabs with high-resource websites, 10 or so, then started flipping among them, dropping into another app then back to Safari, etc. all quickly. It was pretty easy to get the iPad 10 to start reloading tabs. The Air held state far longer. It took me loading apps and sites to a level no sane person ever would on an iPad to finally get the Air to start reloading things.
Those were the only two visible, material differences. Remove those, and they may as well have been the same product.
The Pencil problem, however... So the Apple Store I was at had this big table of iPad 10's, each with a Pencil 1 in a little tray beside it. And not one of the Pencils would work with its iPad. The Blue Shirt told me "yeah, they have to be plugged into the iPad to pair so we only do it when people ask to try it out" ... and as a result, you need that stupid dongle. This is not dissimilar to how I have to plug my Pencil 1 into my 2017 iPad Pro to get it to pair, but that's easy—they're both lightning, you just plug it in, wait a second, unplug and away you go. Easy.
So that's where I part ways with the iPad 10: Managing the dongle/cable dance to pair the Pencil would drive me absolutely nuts. I would learn to live with it if the 10 was cheaper, just due to the otherwise outstanding value of the device, but at its price point, Apple should've found a way to make that process more simple. Pairing a Pencil 2 with an Air 5 is just so much easier, faster, and more intelligent it boggles the mind Apple was willing to settle for the solution they came up with for the 10. Which is sad, really, because again, it's an outstanding iPad in every other respect. If using the Apple pencil is not core to your relationship to an iPad, then the 10 is really great. Modern and fast.