Together with the latest generation of graphics solutions, AMD introduced a low-level API Mantle. Without going into the details of the interface, Mantle reduces the overhead on the graphics processing and improve performance in their respective tasks. Certainly, Mantle cards from AMD will be an advantage at least until DirectX 12 , where Microsoft also took care of organizing low-level hardware access.
But DirectX 12 will be released only in late 2015.
NVIDIA does not deny the effectiveness of low-level interfaces in computer games, but considers waste of resources to create a special API. Instead, NVIDIA decided to focus on improving the performance of DirectX 11. The histogram can be seen below the nine specific DirectX 11 features and in which there are significant improvements in the transition to the latest drivers (New - not yet released version). Also here you can see the result of the benchmark StarSwarm.