There was a review of Ram speed (1333 vs 1600) performance diff, specifically for SB CPUs. It concluded that in normall day-to-day usage there was NO differnces in performance with the cavet that their were a few (very few) softare apps that could take advantage of the added bandwidth. The bottom line was "1600 was the sweet spot SB systems, but should be bought (over 1333) only if the price was nearly the same". My quess is that applies equally to amd and older Intel systems.
Additional comments on DDR3-1333 vs DDR3-1600 for Intel SB CPUs.
For Intel SB CPUs, This has been tempered recently as Intel has stated that OCed Ram voids it's warrenty. DDR3-1600 is OCed ram (exceeds the 1333 spec.
Initially the concern was based on ram Voltage as Most older DDR3-1600+ ram required 1.60 ->1.65 V. This exceeded Intel's spec of 1.50 ± 5% (max Ram V = 1.575V). Newer Ram DDR3-1600 @ 1.50 are now available (Lower CL ratings). While the 1.50 is NOW below Intels max voltage rating, Intel NOW says even at the 1.5 volts the fact that it is above the 1333 voids the warrentee. My QUESS is that the higher freq lowers the On-Die impeadance which increases current is the rational.
Intels "fix" is for users who want to OC ram but an "additional OC warrentee ($25 for the i5-2500K).
PS - I've been running DDR3-1600 CL7 Ram @ 1.60 Volts in my i5-2500k system.