But the PS4s GPU is also better spec'd than a 7850.
You could say the same for the Xbone's GPU - it's a bit beefier than a stock 7770. (12 CUs vs. a 7770's 10) Also, some 7770s have less VRAM (1 - 2GB), so if the tested card was one with the lesser amount, I could see that having been a bottleneck for those benchmarks.
I suppose it's decent for a very general relative comparison, but the finer points of the graphical capabilities won't really be revealed until we see first-party titles that actually push these systems to their limits (and by that I mean a good while after launch), or if 3rd party games start to take advantage of the PS4's stronger specs (higher resolution, locked at higher FPS, more/better AA), and based on what one of the insiders mentioned, it doesn't sound like they're bothering currently, at least not at the outset.
Still, it's plainly obvious that the PS4 has notably better horsepower either way.