I have had an 11" for over 4 years now. It's the first 11" iPad Pro that came on the market. I got it back then for my train commute, so with 4G, and with the base 64GB. I voted 11" here a long time ago as I really loved the format.
However. My eyes aren't getting better. And I feel I'm straining my neck to use it comfortably in a couch. So it is with just a bit, but very little, regret that I just ordered a 12.9". Since I moved into music production with AUM, I also upgraded the storage to 512GB. And kicked out the SIM card, as I have a car now.
I considered the 1TB but seen the fact that everything I do in music works perfectly well in 4GB at the moment on my 11", I see no reason for the extra RAM. 512GB storage will be plenty. I'm not going to future proof, but I will be keeping it for another 4+ years hopefully.