CPU power is a huge factor in Metro Last Light. Watch as the FPS plummet when using older 3+ghz quad-core CPU's.
http://www.techspot.com/review/670-metro-last-light-performance/page6.html
Interesting results, but without knowing how much of the CPU load is due to rendering, and therefore how much of it might be avoided on consoles thanks to their much lower-overhead APIs, it's difficult to draw any solid conclusions.
Further note that Phenoms perform much, much better than Athlons. In particular, the dual-core Phenom X2 3.50GHz performs about the same as the quad-core Athlon X4 3.00GHz. The latter is of course running at slightly lower clocks, but still. A quick look at the Athlon X3 3.10GHz and Athlon X2 3.30GHz confirms that the game is reasonably well multithreated, since the former is a good bit faster in spite of its lower clocks.
All in all, this indicates that Metro Last Light is very heavily cache-dependent. This is further confirmed by the FX-4100's performance at 3.60GHz: it's
much higher than the A10-5700, which has the double benefit of Piledriver cores (vs. Bulldozer) and 100MHz higher clock speed. Developers should have a relatively easier time optimizing memory access patterns on PS4, since every unit shares the same memory architecture and is therefore much more predictable. In fact, it's quite possible that the developers of MLL didn't even bother testing their game on L3-less Athlons. If you look at the results, you'll notice that every CPU with a large L3 cache actually performs quite well.
Meanwhile, the Xbone features fast, embedded SRAM which, if properly used, would be even better.