Is the PS4's GPU being 50% more powerful than that of the Xbox One really gonna affect sales that much? Is it that big a deal?
I guess it is for videophile console gamers (which approaches the whole PC argument that I'll not get into here), but by and large I just don't think it's gonna have an affect on sales between the two platforms. At most we'll see something like the difference between PS2 and the original Xbox, and even then multiplatform games virtually always sold more copies on PS2, and the PS2 vastly outsold the Xbox. The overwhelming majority of console gamers just don't give a shit about FLOPS, or else we'd see a lot more PC gamers and a lot fewer console gamers.
I'm not saying this as a slight against Sony or Sony fanboys either. I'm just saying that if the PS4 does end up outselling the Xbox One and games end up selling more copies on PS4, it won't be because of performance differences. What could hurt Microsoft more are things like marketing, poor messaging, price, or how people perceive Xbox Live against PlayStation Plus.