I don't use a smart phone (cheap mobile without frills works for me), but for tablets I originally preferred iOS for the higher quality of apps and the relative longevity of the hardware. Now that Android has caught up, and at least the Nexus models get support for more than a couple months, I am more comfortable outside of the walled garden. I prefer the relative freedom and greater independence, as well as the lower prices and wider selection of devices.
I would actually like to go back to Linux too, but that is more involved.
