We're really beginning to see more and more 1GB 9600GT cards come to the market, but we continue to see that they offer no real performance increase when compared to their 512MB counterpart.
With the 1GB offering and 512MB model offering the same overclock and the same excellent performing cooler, it's going to be hard to spend the extra money on a 1GB card when the 512MB offering is going to perform almost identically.
With that said though, if you find yourself needing a 1GB card the MSI offering is a good choice for a few reasons; the included HDMI adapter is good which is capable of carrying sound, and the cooler on it, while being dual slot does an excellent job of cooling the card at a reasonable noise level.
The extra $50 - $70AUD that you would spend by moving to the 1GB model could be spent on faster RAM, more RAM, a faster CPU or a number of other things.
The MSI 9600GT 1GB is a good card, but it doesn't represent the best value for money. With that said though, there is no doubt that people out there feel they must have 1GB of graphics card RAM, and if that's the case then MSI could have the card for you here.