Xbox One for me all the way.
I'm not technically minded about system specifications so for me it came down to the very same thought process as I originally faced between the 360 and the PS3.
Would I rather play Gran Turismo, or play Halo and Forza?
Answer to that is Halo and Forza.
As some have said, last time round the PS3 was technically the better machine, but in reality I found the Xbox just felt better. Everything from the menus to the controller just had a more attractive feel. The 360 felt like a progression from what I used to play - the PS3 just felt like going back to my childhood when I played GT1 & GT2.
The recent news about the ONE has cheered me up quite a bit. I wasn't keen on the 24-hour check-in (although it wouldn't impede me) and the DRM nonsense was irritating but again not prohibitive for me. Glad to hear Microsoft has backed down over both.
Next on my list though is the backwards-compatability although I understand this is not likely to change as the systems are developed on entirely different architectures (technical stuff again lol).
My only challenge is games I enjoy playing just now (Forza Horizon, Mass Effect and the LEGO series) don't have ONE replacements, so it's a choice between getting the new FM5 + COD or continuing to play games I still enjoy.