Which video drivers should I install. X.Org X Server or Nvidia Binary Drivers
Perfectly good question.
You can take a look at this site for detailed explanation and benchmarks:
http://www.phoronix.com/scan.php?page=news_item&px=MTM0OTM
But to put it in simple terms, if you intend to play new generation video games on your system, or do any kind of work that puts heavy load on the graphics card, you should use the proprietary nvidia drivers.
Otherwise, you are perfectly fine with the open source nouveau drivers.