While NVIDIA`s binary driver is much faster and better than AMD`s Catalyst, on the open-source driver side is where AMD has been shining. While their RadeonSI Gallium3D driver for Radeon HD 7000 series GPUs and newer is not nearly as well off as their pre-HD 7000 series (R600g) Gallium3D driver, they are making progress. In this article are benchmarks showing the out of the box performance on Ubuntu 13.10 with the modern open-source driver, benchmarks with the latest kernel and Mesa and LLVM, and then the AMD Catalyst driver. A range of modern Radeon HD 7000 and R9 graphics processors were used for this open-source versus closed-source driver testing."
Any major computer upgrade generally requires a full software reinstall too. No so if you heed the advice in the guide to Upgrading a Motherboard without Reinstalling. PCSTATS Tips