What is the difference from an xbox 360 arcade and an xbox 360 pro?

The Xbox 360 Pro Version's Biggest difference from The Arcade version is that it has a Hard Drive, which is mandatory to utilize many of the features of the Xbox, such as the almighty Xbox Live. The Arcade version only comes with a 512mb memory card because it's not meant for storing game saves for the bigger games like Halo 3 or Gears of War, only arcade games, hence the name Xbox 360 Arcade. You can still play games like Halo 3, but a lot of the gameplay features aren't available such as creating movies, or map variants. Of course, If you decide to buy the arcade version now because of a limited budget, you can always upgrade the Xbox later and buy a Hard Drive. Another Difference Is that the Arcade version is the most basic of Xbox's and doesn't output the Hi-Resolution 1080p Graphics that attract people to the Xbox 360, and to get this, you would need to buy the Xbox 360 Pro. The Pro comes with HDMI Cable support so you get the whole deal that the Xbox 360 has to offer.