I considered doing the same, when I saw the 12.9's weight hadn't been reduced, I decided it wasn't for me. Plus, that price, ouch.
I originally ordered the iPhone Xs Max but returned it because it was just too darn heavy (not the size -- I have no problem with Pixel 2 XL which was the same size). I have the original IPP 9.7 and that is about as heavy as I want to go. so I went with the 11.
One other thing I didn't like about the Xs Max was that even though it had a bigger screen you didn't get any more icons per page -- they were just spread out more. From the video it looks like 12.9 has the same issue. Not a major thing but still irritating to me (especially with the $$$ being spent)