In short, why (and when) do i need raw support on my PowerShot?
i. white balance could be set AFTER shooting, in raw converter. A different settings could be tested
i. although ADC in Canon A-series is only 10bit :-( RAW provides wider dynamic range than camera jpeg
i. easier to edit with greatest-quality raw converters
i. in-camera image processing tends to loose saturation badly in deep shadow areas, so you are limited at recovering them using Photoshop Shadows/Highlights function. Fill-light function of raw-converter can be used in case of RAW
i. you can recover more highlights in case of slight overexposure with highlight recovery mode, especially with non-standard lighting
If you don't have an idea what RAW-files are, look here: Wikipedia article about RAW
The the full story HERE