I got the 2017 12.9" because I wanted a bigger display for comics and PDFs. It was great for those tasks and I was using it exclusively for a time but after a honeymoon period of about two months, I found it was too heavy and bulky for me for general reading and bed/couch surfing. Ended up going back to the Pro 10.5 for the most part. Then I got the Mini and it became my most used iPad.
Like I mentioned earlier, sometimes the only way you learn what fits you best is by trying.