NVIDIA Fermi/Kepler GPUs Are The Best Bet For Ubuntu 14.04 Nouveau

Again, these results are awfully skewed compared to using the NVIDIA binary driver due to the reverse-engineered Nouveau driver's current shortcomings.

For devout open-source fans, Intel and AMD Radeon graphics remain the recommended choices until the Nouveau reclocking / performance issues are sorted out. It's unfortunate that at least for the older NVIDIA GeForce GPUs in the out-of-the-box Linux 3.13 + Mesa 10.1 configuration, all my pre-Fermi GPUs were running into issues with the more demanding OpenGL workloads. Besides poor performance, regressions are incredibly common within the Nouveau driver due to being developed via reverse-engineering with no support from NVIDIA up until recently. However, if using the NVIDIA proprietary Linux graphics driver, that's your best bet for HTPC / living room systems, Linux gaming desktops, and other performance-oriented Linux desktops.