I went from the 12.9 2nd gen to the 2018 ipad. I had the 512 though and it was LTE. For what I sold it for, I could've purchased two 2018s and then some.
I did it because I've been wanting to downsize to the 10.5 due to portability, but didn't want to do that with new ones due out this year, so I got the 2018 as a transition pad, and honestly, I really love it. I got me a great stand/keyboard setup, and just have a light case on it, so when I need it to be portable, I can just grab it and go. Honestly, I'm not sure whether I'll go back pro or not. What I thought I'd miss most was the ASK, but the bluetooth keyboard I bought was $12 and looks and feels a heck of a lot like the regular Apple keyboard, which I liked a lot prior to using the ASK. I LOVE the ASK, but it added a lot of weight to the 12.9 pro when I want to take it places.
I miss the screen size a bit, but I think overall the portability factor is better for me right now (and I LOVE the cost).