You want documented ram compatibility. If you should ever have a problem, you want supported ram.
Otherwise, you risk a finger pointing battle between the ram and motherboard support sites, claiming "not my problem".
One place to check is your motherboards web site.
Look for the ram QVL list. It lists all of the ram kits that have been tested with that particular motherboard.
Sometimes the QVL list is not updated after the motherboard is released.
For more current info, go to a ram vendor's web site and access their ram selection configurator.
Enter your motherboard, and you will get a list of compatible ram kits.
While today's motherboards are more tolerant of different ram, it makes sense to buy ram that is known to work and is supported.
The current Intel cpu's have an excellent integrated ram controller. It is able to keep the cpu fed with data from any speed ram.
The difference in real application performance or FPS between the fastest and slowest ram is on the order of 1-3%.
Synthetic benchmark differences will be impressive, but are largely irrelevant in the real world.
Fancy heat spreaders are mostly marketing too.
In fact tall heat spreaders are a negative because they can impact some cpu coolers.
Only if you are seeking record level overclocks should you consider faster ram or better latencies.
Read this Anandtech article on memory scaling:http://www.anandtech.com/show/4503/sandy-bridge-memory-scaling-choosing-the-best-ddr3/1
DDR3 1600 is the sweet spot considering the marginal cost delta over 1333.