The iPad Mini 4. This is my 2018 tablet purchase. And so far, it's the best Android tablet I've ever used.
The Shield is long in the tooth. Although beefy, it suffers what most other Nvidia chipset based tablets do - It's slowed down a LOT. It's too bad too, because otherwise it was almost a perfect Android tablet! 1920x1200 screen, plenty of horsepower for any apps, stylus support, and front facing speakers! Multitasking started suffering though. As did battery life. It shouldn't take 30 seconds to wake the tablet up. Or open an app. Just occasionally though! Just enough to be annoying. And 4 hours of screen on time? Yeah, not overly impressive. Plus the idle battery drain. I love the Android platform, but I think it's really suited for phones more so than tablets.
Of course, I did my due diligence looking into available devices. I wanted something fairly quick, running mostly stock, good screen, small and light form factor, good battery life. It's gonna be used a lot for Lightroom, browsing, reading, and media after all. It's primary purpose should be to get out of the way and let me do those things.
A couple of Android tablets piqued my interest, but ultimately had some issues. Samsung's Tab S3 was plagued with Touchwiz and threatened with lack of updates. The Asus Zenpad S3 ran a Mediatek chipset and was skinned pretty heavily. The Huawei mediapad M3 looked almost perfect, but ultimately lacked some key connectivity features, and once again with the skins. Bah, the last GOOD Android tablet was the Nexus 7 2013.
My final decision was to try out an iPad. The Mini 4 128GB came in at under 500 dollars, features an 8" 2048x1536 laminated display, a good feel in hand, and a very good battery life. Heck, the thing doesn't really drain when not in use, what else could you ask for? Most importantly, it fully supports all of my Google apps. For all intents and purposes, this is an Android tablet to me.
A couple of issues I have with it, and they're only small, and not really the iPad's fault. One - Some apps don't have tablet versions released as of yet, and likely never will. Namely, Instagram. Not a huge deal, but more of an annoyance. It's either use it through the browser, or used a scaled phone version of the app which looks awful. Android handles app scaling a lot better. And two - Lastpass autofill isn't good to go for all apps like it is for Android. I understand app developers need to build autofill in, but it's still annoying that it's not built into the platform.
A small nagging feeling behind me says that software updates might not be so long lived for the product as well. Considering it's initial release in 2015, iOS11 might be the last thing I see for updates on this. Regardless, I'm not tied into Apple's platform, so if I see a good Android tablet released in the next year or two, I may move back over. As for right now, the iPad does everything it needs to do right - It gets out of the way and lets me consume media.