It'll be Android but that's all I know
Like jb99 I'll not buy Apple because they're Apple, they're always playing technology catchup (yes they are) and they don't actually make anything I want, either, which is the main influencer.
Heard the Z10 is surprisingly laggy in the UI from a colleague who tried one and you'll not find me supporting Microsoft.
Plus I'm more than happy with Android, anyway. HTC One looks nice, the S4 is a bit of an anti-climax though has massive CPU grunt like the One does and a fine screen. Most likely will be a Samsung or an HTC, really don't know and not even sure if I care that much any more, either. Not due an upgrade until the next raft of smartphones is released anyway and I suspect that this time next year, maybe end of this year, Samsung, SONY, LG or HTC will be putting something out that shifts the paradigm again for The Next Best Thing so happy to wait, really,