There are two versions of the Yeti. This one, which has an MSRP of about $139, and the professional model, which has an MSRP of about $249, so I'm not sure which one you're talking about that's only $30 more. Perhaps that's the one which comes with the Assasin's Creed bundle? If so, they are the exact same microphone.
The more expensive version has an XLR microphone connection at the very bottom, which allows you to connect to a sound board or pre-amp, like what recording studios use. It bypasses the USB input in this case, and allows the higher end sound equipment to do the analog to digital conversion, rather than the USB input.
Additionally, the more expensive mic allows for 192khz/24-bit recording, which is DVD quality. This one is 48knz/16bit, which is only CD quality. Of course, what you're pumping the signal into, is going to have an impact on your final product too, so just because one buys the higher priced mic, doesn't mean they're going to have a better quality recording.
Hope that helps explain things a little better because I'm not 100% what mics you were comparing.