16Gb (I initially got the 32 but changed it). I don't play a lot of games (and they're not big anyway), or store much data on there. Kindle books I can download when I want and remove them when I'm done with them (besides I like my kindle better for book reading). I stream videos, and use dropbox for my personal files.
The 16Gb will be enough to stock a few videos and books when I travel and don't want to bother with my laptop in the plane.