Unless you are a high-value target, Apple's security seems fairly sufficient for normal use (I have Android ;)). Companies like NSO Group that state that they play both sides without any moral compass seem like a great target for Anonymous or others. Imagine the client list, and banking information as a trail to blaze!
This guy seems to be quite the high-value target to warrant 3 zero-days, on ios no less. edit: What platform would be recommended, if you happen to be a high value target though. Using iOS at least seems to raise the cost of infiltration significantly judging by this http://www.forbes.com/sites/andygreenberg/2012/03/23/shoppin... .
FWIW - I only journal with ink and paper. I never trust digital files, and I sometimes forget how many backups I have of the same photo or other file.