I have an unlocked iPhone 5 that I am currently using with AT&T. I don't really have a preference with platforms but I do like the simplicity and the sheer fact the iPhone works all of the time. My old Galaxy Nexus had issues with apps force closing and such. Android is so much more customizable but hey I rarely used most of the widgets I had.
Without a doubt the iPhone 5 works so much better than the Galaxy Nexus for MFT. One issue that I always had was that the bluetooth streaming always required me to do all sorts of things like turning off bluetooth and turing it back on to work. With the iPhone it connects and plays instantly which I LOVE! The whole reading text thing is nice but if you really want that sort of integration get a Windows Phone. I had a Samsung Focus Flash and it worked the best with the MFT integration.