I mean, the apple pencil can be a nice touch which apparently isn't compatible with the 2.
But mostly it's just a more pronounced form-factor of what the iPad is all about, in particular in comparison to an iPhone.
The bezel to body ratio gets cut in half from about 30% of the body, to about 15%. It's kind of crazy when you think of it like that (instead of screen-to-body), as almost 1/3rd of the body is bezel on the Air models. On the original it was even 37%)
At around 15%, you're approaching the iPad's true form-factor: just one big screen. That's pretty wonderful for consuming content. All this screen real-estate is what sets it apart from say an iPhone for content-consumption, while retaining the notion of it being a lightweight mobile-device you can throw in your bag and whip out easier than a laptop e.g. on an airplane, in bed, in the bus, on a trip, on the couch.
But it's not like you can do all that much extra. For me personally though, reading a digital version to a paper newspaper or even a website always felt a little bit cramped on a regular iPad. It feels most websites and magazines are about 13 inches. For example, The Economist is about 13 inches diagonal. It's very natural to read on the 12.9 inch iPad Pro. Quite alright on the 11 inch, but just a tad too small on the 9.7 inch, requiring more frequent zooming in or alternative views.
The iPad air 3(rd gen) by the way is already a pretty decent middle-ground, at 10.5 inches, nearing a 20% bezel, and very fast for years to come.
But the Pros also have Promotion, which gets you 120 hertz refresh rates. Makes everything buttery smooth. Really not a big deal, but it's one of those things that made me feel like I was using some futuristic device you'd expect in a Star Trek universe. But again, really not a big deal, it's just a feeling. Usually there's some lag, some stutter, some delays. With 120 hertz it feels as if we're moving towards a world in which there is no UI lag and the tech is really futuristic. Combined with an insaaaanely fast device, the only time you get confronted with any latency is when the internet is involved. Not something that'd make me buy the Pro, but it's fun to know that this'll be coming to all normally-priced devices in a few years. You also get more colours, it gets brighter, and there's truetone display. The display is really something else, I'd check it out in stores and see if it matters.
The rest don't matter much to me. FaceID, four really great speakers, ultra fast, better camera, LIDAR, neural engine, I don't really care for. USB-C is a nice touch as I find it's always around for charging. And the magic keyboard is a nice touch together with the pencil, google docs should be a lot nicer with the keyboard and drawing diagrams with the pencil, but then it starts to get quite expensive.
https://phonesized.com/compare/#483,1422,1423