AlucardThe difference is basicly, that the standard version is noise cancelated at the back, so only the part of the mic that is facing your mouth, the front, will pick up sound. The omnidirectional one picks up sound all around, so you can use it to record a conversation that you are having in real life, for example.
Also the enviroment in which you are going to use the mic has a effect on which of these 2 to buy. If you have a very noisy pc for for example, the standard version would pick up allot less background noise.