Well, I'm back from a couple of Malls, a couple because in one there was only the 11 and in the other the 12.9. I played with them for a while, I tried different apps including safari, luma fusion, iMovie , iPhoto, a photo editor, YouTube, Word and Apple TV. I did the test with the IPPs disconnected from the keyboard mostly and the considerations are the following:
12.9
It is actually "heavy" to hold.
Unfortunately I was standing and I could not detach it very much from the table (it was tied with a very short anti-theft wire), but I felt the weight, and it was without any cover.
Using it without some kind of support, even improvised, becomes frustrating after a few minutes and does not make it pleasant to use; however this would not be my use.
The screen .... wow, really wow!
Next to it there was an Air and I ran the same apps simultaneously; what to say, the difference is clear compared to a 10.5 / 11 screen, especially in video content, much more immersive.
11
As with the 12.9, even with this one I was on my feet and couldn't move it much. Without resting it somewhere it takes longer to get tired, but you get tired anyway.
Positive note: holding it in portrait I was able to write with the virtual keyboard holding it with both hands (I have quite big hands), which is impossible on the 12.9.
I was pleasantly surprised by the video editing apps (which I will use), because even if the screen is smaller, it is still pleasant to use; the preview window of the video is smaller, but sufficient (I did not think), at least it can be used in portrait to have it bigger, without sacrificing usability.
Conclusion: I chose the 12.9.
The weight difference is there and you can feel it, but once you place it somewhere, the problem does not arise.
The larger screen, slightly on paper, earns many points over its smaller brother, especially in video content.
The sense of immersion is certainly greater and made me feel a wow effect.
The thing that definitively convinced me, and that I had not evaluated, was the fact that the larger screen is pleasant and usable even at a certain distance. Let me explain, my use of the device will often make me keep it at close range (sofa / bed), but imagine myself doing eg. editing or in any case activities that require hours and a certain attention to detail, with the iPad 11 on the desk, therefore at a relatively greater distance, it tires the view much more and makes the experience less enjoyable IMHO.
This is what I felt while I was standing with the iPad on the table, attached to the magic keyboard. Note. I am 40, with no particular vision problems.
If it weren't my main device I would have chosen the 11 for sure, but ultimately I prefer to give up portability a little in favor of the larger screen size.
That said, I will now proceed with the order, thank you all for your feedback.