Having at various points had a number of iPads knocking around, and also sometimes
reviewing the things for press, I would say:
- Get yourself to an Apple Store, if you have a fairly local one, and actually hold the things in your hand. Play with the thing and move it around. Spend time there. If possible, upload some comic pages or PDFs to a website before you go and read them on the screen. (Safari for iOS will load files with no problems, and although you won't get a comic reader experience, you will see how the screen works for your chosen comic sizes.) Note that Apple has a reasonably liberal returns policy, if you don't like what you buy. Talk to a store clerk about what you want to do, and what options are available in that area.
- Avoid the mini at all costs. It is a DEAD line, and far too small, even if it's light.
- Recognise the new cheap iPad is a good deal, but slightly worse in terms of _some_ aspects of the screen than the iPad Air 2 it replaces. It's more like the iPad Air in terms of feel, and it has far more glare.
- If you're centring on comics reading, an iPad Air 2 might actually be a good cheap choice, note. It's thin, light, solid, and fast enough. However, this is not a good option if you want to do a lot of other stuff with the device, and for a number of years into the future. (My one is fine, but noticeably slow at some aspects of iOS 11. It's starting to struggle a little with some very advanced fare, meaning I reckon it has perhaps another 18 months before that becomes a problem. You should expect an iPad to last around four years in terms of feeling pretty nippy. In terms of build, they're very solid. My original iPad, from 2010, still works fine, although of course won't run any recent apps or games.)
- The two iPad Pros are worth looking at, and are very different in nature. The 10-inch one is really where Apple's tablet line is heading, and there's a larger screen in a form factor little different dimensions-wise from the Airs and new iPad. It's kind of a 'sweet spot' iPad. To my mind, the 12.9 is a bit much – too heavy (although, amusingly, almost exactly the same weight as the original iPad), but YMMV, hence my suggestion you test the things in the flesh.
I would note that price may of course be a factor. In the UK, the 128 GB iPad is £429. A 256 GB 10.5-inch Pro is £709. The 12.9-inch model adds another £150 to that price tag. (There are cheaper models for each, but you'd be nuts to plump for the low-end storage, since you can't expand them. 32 GB on an iPad is a joke, and 64 on a Pro is barely adequate.)
As for Readers, I'd also recommend Chunky. I know the developer is writing a new app right now, and so the original might be a maintenance app for the foreseeable, but it's very good. You can pull down content from various sources (cloud storage; via a browser from the likes of Humble Bundle; local storage, including connected Macs), and there are plenty of options regarding the app's appearance. Beyond that, Comic Zeal is probably the next best option.
One thing that is worth noting: if you go down this route, I highly recommend sourcing DRM-free copies of anything you buy, so you have the option of using whichever reader you choose. Although most companies do offer workable first-party readers for iOS, few are great, and it's not fun when you guy something and it's 'stuck' inside a shitty reader. (Rebellion, natch, has long gone down the consumer-first route, and so whatever you buy from them can be grabbed from the website.)