I think WP8/W8 integration is rather overblown, but the difference in approaches seems to be that Apple and Google are scaling up phone OSes to a tablet OS, whereas MS seems to be scaling down a desktop OS to a tablet, while simultaneously taking the UI paradigm of their phone OS and scaling it up to tablet/desktop.
This means you can dock your Win 8 x86 tablet with a keyboard/mouse and be using the power of full Windows. You can write code for the tablet and debug it from the very same tablet using Visual Studio. You can't really do that with iPads and Android tablets which are relegated to being consumption devices only.
Microsoft sees mobile devices as computers and Microsoft Research is working on a practical IDE for them via TouchDevelop which gives access to most phone features:
There appears to be a vision of a commodity phone running Windows Phone as the "computer on every desk" for the developing world - it's probably no accident that Microsoft teamed up with Nokia.
TouchDevelop is powerful as hell. It's not VC++ by any means, but you can access all of the phones features and data, and develop quite complex applications without actually typing any code. Putting that into Windows 8 Desktop would be a great move, and allowing those scripts into the Marketplace (or someplace where they can be sold and marketed) would be even better. Right now there is a repository for the scripts, but it's sorely lacking in features compared to the Marketplace.
This means you can dock your Win 8 x86 tablet with a keyboard/mouse and be using the power of full Windows. You can write code for the tablet and debug it from the very same tablet using Visual Studio. You can't really do that with iPads and Android tablets which are relegated to being consumption devices only.