iPad mini 5th.
I've had and used quite a few iPad models (1st gen, 3rd gen "New iPad", 1st gen Air, Pro 9.7, Pro 10.5). I've had the mini 2 and loved it. Skipped the 3rd gen and 4rd gen mini for a lack of advantages. And my 2nd gen mini was still fast enough after two or three years. Sadly, it developed a sporadic issue with the touchscreen after I dropped it once. But I wasn't going to buy an "old" 4th gen mini to replace it.
After Apple seemed to have given up updating the mini line for two years in a row (2016 and '17), I turned back to bigger screens and bought a 9.7" Pro and then 10.5 Pro instead.
When the 5th gen mini was announced thoguh, I ordered one and sold my Pro. After receiving my new mini, holding it in my hands and carrying it around, it really made re-appreciate the (mini) form factor and its portability. Going back to the smaller screen and more portable device instantly felt "just right".
I've now ordered a new 4th gen Air, as I can really use the bigger screen school (books). But the mini 5 will still be my primary device - and is my preferred mobile internet device by far. If I had to choose the iPad and the iPhone, I'd give up my iPhone in a heartbeat.