I'll eventually end up with both more then likely if I stay interested in games, but Xbox 1 is the preference.
I have a 360 and PS3 and have done at the very least 95% of my gaming on the 360, all of my gaming friends are on the 360, most of my friends who I live chat with during UFC's sometimes are on the 360. I probably have more time spent playing PS1 and PS2 games on my PS3 then actual PS3 games. Just how she goes.
I think whichever one I buy I will see exclusive games on the other that make me wish I bought that one.
But looking back now that I think about it... if it's like my playstation history I would get the new one when a GTA game came out that kinda made me. GTA 3 made me buy a Ps2, and GTA4 made me buy a Ps3 (okay once that first UFC game came out I would have anyway but that's what it was). But GTA5 isn't even going to be a Ps4 game I heard so not selling my ps3 anytime soon. But if the ah, ps4 wasn't backwards comp. I wouldn't sell it anyway.