Maybe it's just me, but I dislike using a tablet vertically for most use cases. Evan with a 4:3 aspect ratio, it still feels somewhat unnatural and uncomfortable to hold to me and 16:9 is even worse. Reading books is more comfortable to me in landscape, maybe because it looks and feels more like an actual book that way. The other reason I like 4:3 is that 16:9/10 would probably be too wide to comfortably type with my thumbs in landscape view, which isn't something I do terribly often, but occasionally enough that if the screen were any longer it would be a complete hassle. I honestly wish Apple would put the camera along the long end, like a few other tablet manufacturers have done, so that video chatting/conferencing could be done in landscape as well. The only thing I use the iPad for vertically is reading PDFs or Word documents, once again because that's what they physically look like.
Honestly I think 16:10 is the ideal resolution for working on a desktop environment. 16:9 is only good for watching 16:9 movies and shouldn't be used for anything else in my opinion. 4:3 feels pretty good for a tablet, and with the retina display, it's possible to play an HD movie at its native resolution on the screen, so outside of some letter-boxing, there's no real need to have a 16:9 display. Even most websites use a design that assumes a 4:3 display and 1024 pixels of width, and most don't gain additional benefit from wider 16:9/10 displays. I suppose if you hold it vertically, you can get more of the website lengthwise, but once again, I just hate holding a tablet vertically.
A lot of that probably comes down to personal preference, but I'd pick this tablet over many others simply because I feel as though the aspect ratio is better, at least for how I prefer to use tablets.