I had an iPad Pro 12.9” (the 2018 version, not the most recent) and I found it too big, in spite of using a Macbook with a 13” screen and being happy with that. I think, for me, it was that size + aspect ratio... it just didn't suit me, and it was too heavy to cart about so it always stayed home. Sold it on and went with the Air 3, and that has worked well. If I upgrade again it will be to the 11”, but at this time, 10.5” is just fine
