Here’s my experience with iPads:
1. Third gen iPad - Really amazing screen for the time. Apps and interface were so much better than the Android tablets I had been messing around with. It was more than a little laggy in the performance department and was a bit of a chunky beast. Also, despite spending all kinds of money, including buying the powered Evernote/Adonit stylus, I never did find anything that worked well.
2. 9.7” IPad Pro - Almost everything I ever wanted in a tablet. Great apps, beautiful screen, fast/responsive, excellent stylus support in the Apple Pencil. However, I found it just a little too small for reading and marking up some types of business documents and I didn’t want to move to one of the original 12.9” iPads because they were just mammoth.
3. 2018 12.9” iPad Pro. Checks all of the pro boxes mentioned above with none of the cons mentioned above. After more than 7 years searching (including my brief dalliance with android tablets), I really have found the ideal tablet for me.