Sweet spot: iPhone Smartphone, Windows 8 Tablet
I'm a big believer in diversifying your electronic gadget portfolio as long as the devices all play fairly nice with each other. Locking yourself into one single ecosystem just doesn't offer many incentives in today's fast paced mobile tech industry because none the major players offer you a level of integration so tight that there are any clear advantages. They try to tighten things up using proprietary cloud services and email but to be honest neither hold any clear or earth shattering advantages over the independent players out there, ie. Dropbox as just one example. There's also very little stopping you from using Gmail on a Windows device. With that in mind I think I've hit the sweet spot for a platform agnostic approach to mobile devices for 2013-2014:
Smartphone: iPhone 5. Best track record for the last 3+ years solid in hardware and OS reliability and customer satisfaction and still remains the #1 platform for developers and the best app store on the planet. The only company that enjoys NO carrier interference for OTA updates. Zero fragmentation.
Tablet: I'm convinced that once the Bay Bridge CPU's are inside of full version of Windows 8 tablets this year(meaning not RT) that's going to be a slam dunk. iPads are great tablets but at the end of the day a mobile OS can't compete with being able to have full computing power and full sized computer applications on a tablet form factor while also getting the better battery life of traditional tablets. This is one area where Apple badly needs to catch up.
I'm envisioning my next 18 months minimum so far as consisting of an iPhone and one of the upcoming Windows 8 Tablets running a Bay Bridge processor as my two main mobile devices.