HTC One M8 just for its body and not whats on the inside, you ought to know that the Windows Phone 8.1 version is now available. Its called HTC One M8 for Windows Phone, very original, we know, and it has all the same hardware, build quality and design as the Android version.
The Windows Phone 8.1 version has the latest from Windows Phone, like Cortana and the notification panel, but HTC has worked with Microsoft to make some features uniform between the two devices. One standout feature of the One M8 is the dual camera, which allows you to take pictures and adjust focus later. That feature works on both Android and Windows Phone versions.
HTC also worked to create a Blinkfeed app due to the restrictions on Windows Phones interface. While its not a home screen slide away, you can put the Blinkfeed app on your Live Tile home page and get quick access to your favorite feeds.