I was so tired of IOS. I was absolutely fed up with iTunes and I couldn't stand how hard and inefficient it was to do basic business related stuff on my iPhone. I produce music and it was terrible on iPhone to send emails with music attached or save music files I would need from artist or partners. I would always have to use third party apps that would crash and it became unbearable so I switched to WP. I use OneDrive all of the time so it only made sense to use the phone that has it completely integrated.
Sending email it's great on WP but email management is pretty poor. Hopefully Windows 10 introduces a better email app.