With xf86-video-intel 3.0, SNA is the default means of 2D hardware acceleration after replacing UXA, but Ubuntu Linux for several releases has already enabled SNA by default for better performance. GLAMOR remains just an experimental option and it's not clear what Intel's end game will be. The benefit of GLAMOR is relying upon GPU-agnostic code for 2D acceleration that leverages the OpenGL driver: it's simpler, saves development time, and can deliver decent performance. But GLAMOR's maturity comes after Chris Wilson and others have invested significant amount of times writing the huge "Sandy Bridge New Acceleration" code-base with the fine-tuned back-ends for the different generations of Intel hardware. For the near future, Intel will stick with SNA by default.
A wide variety of Linux 2D benchmarks were done to stress the UXA, SNA, and GLAMOR back-ends of the Intel driver. There were X11, Qt, Cairo, and GTK benchmarks run via the Phoronix Test Suite on this Ubuntu 14.04 Intel Core i7 4770K Haswell system.