Probably both, but they seem to be preferring iOS. It could be they see Apple as less of a competitor then Google or maybe just because iOS is easier to deploy in an enterprise. Fewer models to validate in the environment and more management features. Not sure at Microsoft, but most enterprise environments give very few Android options to choose from. Many always allow the latest iPhone, but take a long time to approve new Android devices forcing employees in to an older model.
My thoughts exactly!