The synthetic benchmarks don't translate particularly well to real-world use, as the performance differences typically are much smaller when you look at actual applications. However, these benchmarks show the difference in memory performance, which does in fact exist.
SiSoftware Sandra 2008
It is obvious that faster clock speeds and shorter timings result in increased performance. Almost all of the synthetic tests scale linearly, although DDR3-1333 at quick timings isn’t too far away from the DDR3-1600 settings. We’d say that going for DDR3-1600 doesn’t make much sense unless you need the wider memory clock speed range to support your overclocking ambitions.