As to those number PC 3200, 2700 etc.... These represent the number of bits in millions or MBits. since there are 8 bits in a byte, a PC3200= 400MByte/sec 2700=333 etc... just divide the number by 8.
You will also note that depending on the quality of the RAM you will have diferent specs such as 8,3,3,3,
These number represent access time.
Imagine each RAM as a grid with columns and rows and each intersection point being a memory location.
These numbers are CAS and RAS or Column Address Strobe and Row Address Strobe. They represent the number of clock pulses required to access that particular row/column address.
So even if you have 2 sticks working at the same frequency, depending on the brand/quality of the stick it will take more or less clock pulses to access an address point. The lower these numbers, the better.
Since the row and column are not addressed at the same time with row being the first one, another spec is the CAS latency or the number of pulses between a row address and a column address. You can find a little more info here:
Use any search engine and type your question (e.g. RAM specs explained) and you will end up with several pages giving you info.
Hope this helps