Personally, I'd keep it simple and never buy below 32. However, in terms of choosing one over the other? If you mostly stream, and don't have space consuming games (i.e. you're fully cloudy), then 16gb will probably do. If you often find yourself out of fast internet coverage for short periods, then I'd recommend a minimum of 32. For what I do, with the 32, I find that on a typical 2-4 week trip, I can:
- Take 2-3 movies
- Sufficient music for me (I don't have a huge library, and like to discover new stuff through Spotify)
- Sufficient books
- A few TV programmes, downloaded from BBC iPlayer or 40D.
With a 16gb tablet, I'd struggle with that. Of course, if most of my businesses was in Europe or the US, perhaps a 16gb model would do (a lot our customers are in some of the less connected bits of Africa), but I would always go for a 32gb minimum.