I love the Windows Phone and especially my Lumia Icon. With that said, last week I had to switch to an iPhone 6+. Here are the reasons:
1) Major apps that I use, ie. Chase Bank, are withdrawing support
2) Many apps that would really help are not present on WP but available elsewhere. For example, ADT Pulse remote monitoring, our community gate system, a true Starbucks app, to name just a few
3) I am a Realtor. None of the apps for the MLS are on the WP, but they are on iOS. The main one is the lock box key. I can open the from my phone, but the company was refusing to put out the same app on WP. We also have apps that access the MLS from anywhere and provide property details when at a specific location. None of this is even on the blueprints for WP
4) It's great that Office is an integral part of WP but it's not nearly as clean as the iOS programs now available. I have an Office 365 account, and perhaps the implementation on WP will improve, but now it's awkward to use.
I love the whole integrated Contacts ( People ) system in WP. I really miss that on the iPhone 6+. I saw this morning that Outlook was created for iOS, and I installed it. Sadly, I have two Exchange accounts, which Outlook in Windows handles beautifully. However, it appears that I can't add the second account to the iOS device. It only supports the main O365 account.
I want to see WP succeed. I love the devices and OS, but without support from the major service providers ( banks, retail outlets, professional groups ), I don't see it growing. Also, the carriers clearly sandbag it, at least in the US. With these problems, we as independent developers, really don't have much opportunity to create new programs to fill the major gaps still out there.