Comparing the relative speed of cards can be difficult. Many benchmark tests focus only on specific display or model types.
For instance many 3d benchmarks focus on shaded views of mesh models with or without textures. These benchmarks tend to favor the Gamer cards (GeForce and Radeon) card. This type of shading is used heavily in rendered viewport display and other Rhino display modes that do not display edges. Here is an example of this:
http://www.videocardbenchmark.net/high_end_gpus.html . Looking at this chart you would be crazy to buy anything but a GeForce card if performance was important. The $5000 K6000 shows up 7th in the list with 5 sub-$1000 cards ranked a head of it.
But, Rhino also needs to display many curves and edges which are OpenGl vector drawing. If benchmarks are focused more on this type of engineering display, the relative speed of cards can be quite different: http://www.tomshardware.com/charts/workstation-graphics-2013/20-OpenGL-SPECViewperf11-Solidworks-03,3296.html . Now the fastest GeForce does not show until card 25 of the fastest cards.
I would expect Rhino to benchmark out more like the engineering benchmarks. The HoloMark 2 benchmark may show this also.
This has been a pattern we have seen for years from the video card companies.