I have an IPhone 6 as of late, I've read their documentation about security, performance, etc. They seem to be serious about all that stuff. I like it, but what I dislike is the "walled garden" approach to the flexibility of intalling apps and the like. I personally don't want to be treated like a simple-minded individual who doesn't know how to operate a phone. Believe me, I do.
If I were to get a new phone, though, I'd probably get Galaxy S7 rooted with cyanogenmod (when the mod comes out)