Results: Borderlands 2
In Borderlands 2 we see a .1 FPS difference between the rendered frame rate and the practical results, while 2.4 FPS separate the Radeon cards. Fraps is even more optimistic than either FCAT-based measurement.
As we look at frame rates over time, it's obvious that these configurations perform similarly. However, we see some frame rate spikes on AMD's hardware that isn't reflected in the practical result when drops and runts are taken into account.
Frame time variance at these high frame rates is minimal.