Since the iPhones have been getting so much bigger (I have a 7 Plus), I haven't had much interest in the minis. The next step for me is a 9.7" to 11" iPad. 12.9" is too big for me for an iPad, but I have a 12" MacBook.
Coming from an iPad 3, I'm very tempted to get the Mini 5 cellular for its price point and practicality, but the 11" iPad Pro is very appealing to me as well. If price is a non issue for sure I'd get the 11" iPad Pro, but considering that I'm paying a laptop premium price to get a top end iPad is somewhat off putting.
So get the 10.5" iPad Air then. It's a HUGE upgrade over the iPad 3, in just about every way, and it's much, much cheaper than the 11" Pro. Or else do what I did and get the iPad Pro 10.5" from the Apple refurb store, or on closeout from a retail store. The iPad Pro 10.5" is superior to the Air in most ways except the SoC, which is mildly faster on the Air 10.5" vs. the Pro 10.5".
Also, with the Apple Smart Keyboard for the Air/Pro 10.5", it has become a partial laptop replacement for me. The keyboard is 18 mm full-size, and has a decent feel and key travel. The keyboard on the 9.7" Pro is too small, and the 9.7" Pro is not a great value anyway in 2019 IMO.