Get as close to the OS vendor as possible. Less deviation from original intent, presumably more focus on engineering (yes, I know Nexus phones aren't made by Google, but by various vendors who also make their "own" versions), and you get updates much faster in the event of a security concern.
I have an S3 - I knew I was getting outside of the Android ecosystem to some degree when I first powered up the phone and saw the AT&T logo splash screen. Then you get into the phone and see all the cute little Samsung apps. Reminds me of buying a Windows PC :-)
You can regain some of what I described above by rooting and locking your phone down.
However, as you described your needs, an iPhone is ideal. An Android phone gives you a lot of power, but it doesn't sound like you need that much power, and for most people, security trumps customization.
I have an S3 - I knew I was getting outside of the Android ecosystem to some degree when I first powered up the phone and saw the AT&T logo splash screen. Then you get into the phone and see all the cute little Samsung apps. Reminds me of buying a Windows PC :-)
You can regain some of what I described above by rooting and locking your phone down.
However, as you described your needs, an iPhone is ideal. An Android phone gives you a lot of power, but it doesn't sound like you need that much power, and for most people, security trumps customization.