I might be able to shed some light on this. I took a look at both the M4 11” and 13” today on the Apple Store. For context, I’ve gone from a 10.5” iPad Pro to a M1 12.9” Pro with Magic Keyboard.
The new M4 13” is noticeably lighter when you pick it. I could defo notice the difference in weight, even when in the Magic Keyboard case. However, I thought maybe the lightness/thinness would make the 13” nicer to hold as a tablet. At the moment, I find the M1 13” too heavy and unwieldy to hold. But I still find this to be the case with the M4. The lightness helps, but I still find the dimensions too unwieldy to hold as a tablet when reading, etc. I think it’s a device made to be used in the Magic Keyboard. As a side note, when you do a bird’s eye view of the M4 13” in the space grey Magic Keyboard, I got major 12” MacBook vibes.
Overall, I found the 11” much nicer. Coupled with the Magic Keyboard, it’s not too heavy to bring around and feels solid. I didn’t find a huge difference between the MiniLED and the OLED but then again I didn’t compare them side-by-side. But I did find a huge difference though between the OLED and the IPS display of the iPad Mini/Air.
So, to summarize, I think the 13” is still a device that’s best suited to be kept in a Magic Keyboard and use on your desk, etc. The 11” is much more comfortable to hold in your hands for reading, etc but you will get a more cramped experience when typing on the keyboard.