How much faster is the black than the blue? I'm pretty sure the black has more cache than the blue but whats the difference? Is the black worth the extra $20?
How big of a difference does cache size make?
Not much difference, velociraptor what has 16MB of cache is extremely fast. The Cache size difference is really small performance gain, more is better, but you wont really notice it.
However, looking at blue vs black, the WD black has a longer warranty and higher grade components in it, and integrated dual processor, making in superior. (simply put, The chipset on it, is better)
If you are looking for a major speed boost, get an SSD or velociraptor.
*you wont really see the difference in games, only faster loading times.