One of the main benefits I keep reading about of using ACR and RAW file formats is that you can always change the white balance of an image after it is taken. I just used Bridge to open some JPG files and I was able to change the white balance on these as well. What is the difference? Is it not allowing me the full adjustments that I would have if it were a RAW file?
The short answer is Yes. A JPEG has already undergone conversion from a larger linear file with a measured white balance, so any consequent adjustments on the cooked file will not produce as smooth and accurate a result. I'm sure someone else will provide you with the long answer.
What Yammer P said.
Add to that the fact that JPEG has undergone lossy compression, which further reduces the accuracy of the image data.
JPEGs have their uses, but if your storage and processing resources are up to it and your software supports them, it's probably a good idea to shoot raw images.