Here's a very informative link about it.
http://www.hardwaresecrets.com/article/Everything-You-N...
That being said, in general, if your motherboard will support quad channel, you should probably plan your memory purchase to enable it. Will it help your computer go faster? Maybe. The whole point is that you want to maximize your available bandwidth between the CPU and the memory banks.
In a single channel setup, there are 64 data wires between the CPU and the memory.
In a dual channel, there are 128 wires.
In a triple channel, there are 192 wires.
In a quad channel, there are 256 wires.
That means your maximum bandwidth is a calculation of the data rate x bits transferred per clock. So, assuming in a dual channel setup, vs a quad channel setup, assuming that your memory modules are the same, a quad channel has twice the potential bandwidth available. Whether your processor can utilize that extra bandwidth depends quite simply on the workload. Transfers from memory to CPU are already pretty fast, waiting for the hard drive however (even a SSD) adds an order of magnitude in wait time.
Hence, when enabling quad channel (assuming the CPU is quad channel capable), you are talking about -potential- bandwidth, and if you're buying -new- already, you should plan to buy to enable the maximum speed of your system (unless it's stupidly expensive!).
Given the memory you listed, you didn't specify the motherboard or the processor, and not all processors support quad channel memory. Just because it has 4 slots, that doesn't mean it supports quad channel memory. Currently, ONLY INTEL LGA2011 CPU's support quad channel. That means Sandy Bridge-E/EP processors, or Xeon E3/E5 series of the Ivy Bridge-E/EP and Haswell E/EP.
The Sandy Bridge-EP is reasonable ($200-$300 USD) on eBay, the Ivy Bridge/Haswell versions are... well... rather expensive for the fast ones. 1.9Ghz Haswell E for $250 to start. Faster == more $$. 3ghz i7-5800 series are running around $800.
So - assuming that your machine is indeed a standard desktop (not a highend workstation and/or server) you're running a stock dual channel CPU/MOBO, like a Core i5/i7 series consumer system, with 4 slots available. As such, calculating the rough rating to compare is a matter of dividing the raw MHZ speed by the CL timings (in this case, both are CAS 7). In that case, the 1600mhz TridentX memory is indeed faster than the 1333mhz Ripjaws memory, and it has the advantage of leaving two extra slots available should you decide to increase your memory capacity (you would just buy two more 1600mhz/cas7 sticks - preferably the same brand/make).
With the 4x2Gb you would have to buy all new sticks to increase capacity.
So - go with the TridentX.