The funny (sad) part is that there is no correct answer usually - there will always be contexts in which you would be better off with the other side. Generally, I like to think of it this way:
- Do you want a tablet that can act as a laptop if needed - 11" iPad Pro
- Do you want a laptop that can act as a laptop if needed -12.9" iPad Pro
I have a 2021 12.9" iPad Pro and an iPad mini. The larger display of the iPad Pro is very nice, but I discovered when I picked up the iPad mini on a whim was that I reached for it 75% of the time. I learned that what I valued in the iPad was being able to pick it up and use it without thought as I use it without the keyboard most of the time. I found the things that worked best on the larger iPad (Sidecar to Mac, streaming video, productivity) were not the things I used most often and things like reading books or manga I didn't enjoy on the 12.9". It's a combination of the weight and size that make it a bit more of an effort and I don't want to have to carry a stand around with me.
Given this, I'm waiting to see what the future of the iPad Pro and Air lineup looks like. I honestly think my ideal future is a 11"-sized iPad as my main personal computer for all iPad-y things and then perhaps a rumored future 14" + "iPad Studio" for art and other uses (streaming, external display) etc when I can find good deals.
I know
@rui no onna has mentioned that alternating upgrade cycles can help offset the ever growing up front costs.