Lorenzo Franceschi-Bicchierai, writing for Motherboard:

This is the fundamental difference between Android and iPhone. When there’s a bug on iOS, Apple patches it and can push an update to all iPhone users as soon as it’s ready, no questions asked.

When the same thing happens with Android, Google patches and then… god knows when the AT&Ts, Verizons, HTCs, and Sonys of the world will decide it’s important enough that they should care and send you the update with the patch (though to their credit, they’re starting to care, mostly because having an updated OS is now seen as a competitive advantage). Hell, even Google-owned Nexus phones, which the company has full control over, haven’t been patched for Stagefright yet.

There are perfectly fine reasons to prefer Android. Security isn’t one of them.