Mobile
phone sims generally aren't the answer for larger amounts of data and unless you have a specific data sim you are limited as to how you use it. In
Europe at least
wifi is nearly always going to be better. I appreciate that isn't the case in countries that skipped standard telecommunication infrastructure like
Morocco for example.
I have unlimited data on my phone but it's useless if I want to do something the computer as normally tethering isn't allowed when using a phone sim abroad.
Add to that mobiles and tablets are very limited in what they can do compared to a computer (especial iOS devices as I'm finding out), so I'd never want to completely give up being able to get hold
wifi when available.
I have taken a look at the Ubiquiti Bullet, it looks interesting, but it seems you're limited to either 2.4ghz or 5ghz, so whichever one you buy you'll be missing out on a load of wifi hotspots that are on the other different frequency. It looks like its got a built in router too which would give me cause for concern as I'd just prefer it to pass the raw data to my own router.
Anyway, some good stuff in this thread even if it has got a little side-tracked.