Phoronix reports there's room for improvement in the power management of AMD's Linux graphics drivers, you can check it out over here.
"Today on Phoronix are not only new benchmarks of the
proprietary Catalyst graphics driver compared to the open-source Radeon
Linux driver alternative when looking at the OpenGL frame-rates, but
also metrics on a number of other fronts. In this article is a graphics
driver comparison when looking at the system power consumption, GPU
operating temperature, and CPU usage too. The results are quite
interesting and not commonly looked at on Phoronix or by users."