Don has a Windows Phone 7, he's noticing that the security updates are about to run out, and he's concerned about security. Leo says that it's not really cause for concern. He's not using the latest or greatest, but it's such a small market share, that malicious software simply isn't attacking it. Don would like to switch to the iPhone. Leo says he can. It's a good next stop in the smartphone game, and it's very secure. It's not perfect, but at the crossroads of security and convenience, Apple does a great job. In general, smartphones are very secure anyway. Malware is always caught quickly and cleared or repaired. In extreme cases, apps are merely "killed" by the publisher remotely if the app is compromised.
The other issue though is privacy, which is actually worse than it is for desktop computers. Law enforcement can get information on him without a warrant based on the phone. It happens a lot and is a chief crime fighting tool. They can also get metadata on who he's calling and when. He can always turn on encryption and Leo says he should just in case he loses the phone.