I'm going to get both, but at launch I'm going to go against the grain of the rest of this thread - I'm going to be picking up an Xbox One. (In truth, I'm getting both on launch day as I need 'em for work, but if I was only buying one, it'd be the Xbox right now.)
The PS4 is actually the console that I want more and the one that I think will come out of the generation on top, the better machine - but at launch the games available just don't interest me. On the Xbox there's three things I know I want absolutely - Dead Rising 3 (series fan), Killer Instinct (big fighting game nut, so the first one of the new gen is a must for me) and Forza 5 (I love my proper racers, and while I'll also be getting GT5 in December I also am very excited for this.) The PS4 has definitely got the tech and will have the games a little further down the line, but none of those launch games really excite me. I was really bummed out by Knack in particular, as I thought that looked fascinating, but then I played the most mind-numbing, boring 40 minute demo with a 15-20fps frame rate. I'm still gutted about it, really.
I think this is a case in general for me; I'll take Halo over Killzone any day, and so on and so forth. Sony is doing amazing work with indies and has the better machine, but until we get some stuff from Santa Monica or Naughty Dog especially or until the third parties understand the hardware to the point of getting decent parity with the PC I'm more interested in what Microsoft's in-house stuff is offering. So I think initially I'll be on the Xbox, and will transfer to the PS4 more fully as games start hitting in earnest, especially the stuff from 3rd parties in Japan.
With the confirmation that Watch Dogs is only running on 30fps on both consoles with the PC version able to reach 60 on good enough hardware, I'll be getting games like Watch Dogs, Assassin's Creed and Battlefield there. I'm not interested in COD. Titanfall is a must-have, and the best pre-release game I've played in years - but again, I'll wait and see how the Xbox One version of that shakes down first, as that might again be a PC scenario. Unlike Battlefield, it has that sort of COD feel that's designed around a console, though.