The conventional wisdom has been “don’t use EXA, it’s slow.” With recent changes in the xserver and drivers (specifically radeon), it actually works quite well and in most cases is as fast or faster than XAA (especially with AA text). As an added bonus, EXA supports transforms, so you get nice fast screen rotation via xrandr. If you have a “MigrationHeuristic” option in your configuration, remove it. That option was a workaround that basically disabled acceleration to work around the lack of EXA composite support in the drivers and poor performance in the EXA core. These have both been largely addressed in the drivers and xserver git. To reach this wonderland, you’ll need the radeon driver (xf86-video-ati) from git and the xserver from git for optimal performance.
On a related note, to clear more confusion, neither EXA nor textured video use the mesa OpenGL 3D drivers. While EXA and textured video use the 3D engine, they program it directly from the driver, so there is no dependancy on the mesa driver for EXA and textured video.