I was considering whether I could keep my current tariff, and order the phone on the apple upgrade plan (so that it includes apple care for repairs etc). It would work out a bit more than a new contract from O2, though, but that would lock me into 24months (which is probably fine), and wouldn't come with apple care (again probably OK; it would be on my house insurance, but the excess would probably be too much to make a screen repair worth it, so undecided about this one).
also, my current tariff is a simple pay monthly one, that includes only 500mb of data. That's fine for what I use now. But if I had 4G, I wonder if it would use more? I read very conflicting advice about that on the internet. Some say it goes up just because you use it more when it's fast. Or because it sends you higher spec ads, once it detects you have 4G, etc. In the end, 500mb might not be enough, and if I upgraded that tariff, as well as buying from the apple store on their plan, it would probably be notably more than just getting an O2 contract.
I'm also wondering if the fact that there's a good camera would mean that I'd take a lot more pictures than before. (And of course they'd take up more memory anyway, as they're twice as high pixel count as my old one). I have a 16GB one now, which gets full easily. I hoped 32 might be enough for a new one, but it sounds like it won't really be - if the photos are double the size, I'll be as close to filling that one up soon as I am this one.
And then still the question of whether the plus size is too big to use comfortably...
Do either of them have the gorilla glass that is supposed to stop them cracking? I'd really rather not have to use a case, but I guess it's sensible. A screen protector if needed, but they're so big already that adding a rubber bumper case or whatever would make it huge!