In terms of overall gaming performance, the graphical capabilities of the Nvidia GeForce GTX 780 are significantly better than the Nvidia GeForce GTX 660 Direct CU II Edition.

The GTX 660 has a 117 MHz higher core clock speed than the GeForce GTX 780, but the GeForce GTX 780 has 112 more Texture Mapping Units than the GTX 660. As a result, the GeForce GTX 780 exhibits a 87.3 GTexel/s better Texture Fill Rate than the GTX 660. This still holds weight but shader performance is generally more relevant, particularly since both of these GPUs support at least DirectX 10.

The GTX 660 has a 117 MHz higher core clock speed than the GeForce GTX 780, but the GeForce GTX 780 has 24 more Render Output Units than the GTX 660. As a result, the GeForce GTX 780 exhibits a 17.9 GPixel/s better Pixel Fill Rate than the GTX 660. However, both GPUs support DirectX 9 or above, and pixeling performance is only really relevant when comparing older cards.

The GeForce GTX 780 was released less than a year after the GTX 660, and so they are likely to have similar driver support for optimizing performance when running the latest games.

The GeForce GTX 780 has 1024 MB more video memory than the GTX 660, so is likely to be much better at displaying game textures at higher resolutions. This is supported by the fact that the GeForce GTX 780 also has superior memory performance overall.

The GeForce GTX 780 has 144.2 GB/sec greater memory bandwidth than the GTX 660, which means that the memory performance of the GeForce GTX 780 is massively better than the GTX 660.

The GeForce GTX 660 Direct CU II Edition has 960 Shader Processing Units and the GeForce GTX 780 has 2304. However, the actual shader performance of the GTX 660 is 991 and the actual shader performance of the GeForce GTX 780 is 2078. The GeForce GTX 780 having 1087 better shader performance and an altogether better performance when taking into account other relevant data means that the GeForce GTX 780 delivers a massively smoother and more efficient experience when processing graphical data than the GTX 660.

The GeForce GTX 780 requires 250 Watts to run but there is no entry for the GTX 660. We would recommend a PSU with at least 450 Watts for the GTX 660 and a PSU with at least 600 Watts for the GeForce GTX 780. The GeForce GTX 780 has been recommended a PSU with 150 Watts more than the GTX 660. The difference is significant enough that the GeForce GTX 780 may have an adverse affect on your yearly electricity bills in comparison to the GTX 660.