Which gpu is better 9600gso 768mb or 9600gt 512mb?

Nvidia 9600GSO cause it has more stream processors, the difference is very less, more ram will only benefit you if you resolution is higher or you have multiple display depending on what you are using the card for, either would be fine, but if you are using this card for multimedia it would be fine for most tasks, both of the cards will play older games more efficient and if you have integrated graphics, it play newer game more effieciently because of direct x versions compatibility. 9600GSO wins

By putting your camera into shutter speed priority. this way camera will automatically adjust the iso and the aperture in accordance with the environment.