As of yet, none of them. I am looking at the new iPad Air with 256 GB but I may wait a few weeks to see if any problems pop up. I'll admit I'm afraid of how thin these things have become, especially with the Pro models having problems being easily bent. I'd prefer something a couple of mills thicker with more battery space rather than trying to impress people that it is less than 7 mm thick. My friends, or me for that matter, don't care how thin it is after a certain point.
There really is a such thing as too thin. With the new iPad pro’s being 5.9mm, that is really thin for sure.
As long as you don’t sit on one you’ll be okay. I have never seen a real bent iPad in person though. I’ve handled at least 10 iPad Pro 3rd gens, and I’ve owned 3. Never seen a bent one.
Getting back on topic, it seems that the iPad mini 5 is extremely popular! Especially with the specs it has.