There is nothing called a sweet spot in RAM's. The 1600MHz will provide marginally better performance than the 1333MHz in the real world. But the higher frequency of 1600MHz would help when overclocking. It would provide a lot more room to the user than the 1333MHz. About the timings i would say it would be better if you had read all the long nonsense that people told you, you would have got it by now. The first value is the most important one. Which is called the CAS Latency (CL).
According to Wikipedia CL is :
The time between sending a column address to the memory and the beginning of the data in response. This is the time it takes to read the first bit of memory from a DRAM with the correct row already open.
For more info:http://www.hardwaresecrets.com/article/26/
I know its long, but to know more you would have to read more.