To repeat what has been proven in tests in the labs of the photo mags, some cameras can produce a better jpeg than conversions done later through software and that is the reason for the choice RAW + jpeg in a lot of cameras. This means that if you make no adjustments and simply do a conversion from raw through software, the resulting jpeg will NOT equal the quality of the jpeg produced directly from the camera.Originally Posted by Erik Stiegler
As to adjustments they are not equal either. The difference is for example, working in RAW to improve the exposure in a dark area and the consequence is blowing out the highlights. In jpeg you would work on the dark area selectively using Curves and the highlights would not be affected at all.
Practical advantages have already been mentioned.
Ronnoco