Axonn, if comparing just the latencies, then yes - the lower, the better. However, everyone knows that RAM quality isn't measured by just latency; and the price of RAM should never be a means of quality measurement.
While the typical latencies for DDR2 were 5-5-5-15, the standard latencies for the DDR3 are 7-7-7-20 for DDR3-1066 and 7-7-7-24 for DDR3-1333.
DDR3 latencies are numerically higher because the I/O bus clock cycles by which they are measured are shorter; the actual time interval is similar to DDR2 latencies (around 10 ns). As with earlier memory generations, faster DDR3 memory became available after the release of the initial versions. DDR3-2000 memory with 9-9-9-28 latency (9 ns) was available in time to coincide with the Intel Core i7 release. CAS latency of 9 at 1000 MHz (DDR3-2000) is 9 ns, while CAS latency of 7 at 667 MHz (DDR3-1333) is 10.5 ns.
Basically, the lower the CAS the faster the RAM will process data based the DDR level. It is independant of the MHz to a point. Examples, DDR3 is faster than DDR2, DDR3 1333 Cas6 is faster than DDR3 1600 Cas9... etc.
Awwww... ***... do I have to worry about voltages too??? I can't have RAM running at different voltage than CPU? Since when? For example I got a Core2Duo running at different voltage than the RAM right now.... *scratches head*.
With the newer Intel chips, they have a memory controller on the chip which puts a limit on the voltage requirements for this reason. It is something relatively newer requirement on the Core i3, i5, i7's.