The GeForce GTX 770 has a 131 MHz higher core clock speed than the GTX 670, but the GTX 670 has 96 more Texture Mapping Units than the GeForce GTX 770. As a result, the GTX 670 exhibits a 71.1 GTexel/s better Texture Fill Rate than the GeForce GTX 770. This still holds weight but shader performance is generally more relevant, particularly since both of these GPUs support at least DirectX 10.
The GeForce GTX 770 has a 131 MHz higher core clock speed than the GTX 670, but the GTX 670 has 32 more Render Output Units than the GeForce GTX 770. As a result, the GTX 670 exhibits a 25.1 GPixel/s better Pixel Fill Rate than the GeForce GTX 770. However, both GPUs support DirectX 9 or above, and pixeling performance is only really relevant when comparing older cards.
The GeForce GTX 770 was released less than a year after the GTX 670, and so they are likely to have similar driver support for optimizing performance when running the latest games.
Both GPUs exhibit very powerful performance, so it probably isn't worth upgrading from one to the other, as both are capable of running even the most demanding games at the highest settings.
The GTX 670 has 1024 MB more video memory than the GeForce GTX 770, so is likely to be much better at displaying game textures at higher resolutions. This is supported by the fact that the GTX 670 also has superior memory performance overall.
The GTX 670 has 160.2 GB/sec greater memory bandwidth than the GeForce GTX 770, which means that the memory performance of the GTX 670 is massively better than the GeForce GTX 770.
The GeForce GTX 670 SLI has 2688 Shader Processing Units and the GeForce GTX 770 has 1536. The GTX 670 having 1152 better shader performance and an altogether better performance when taking into account other relevant data means that the GTX 670 delivers a massively smoother and more efficient experience when processing graphical data than the GeForce GTX 770.
The GeForce GTX 670 SLI requires 340 Watts to run and the GeForce GTX 770 requires 230 Watts. We would recommend a PSU with at least 550 Watts for the GeForce GTX 770, but we do not have a recommended PSU wattage for the GTX 670. The GTX 670 requires 110 Watts more than the GeForce GTX 770 to run. The difference is significant enough that the GTX 670 may have an adverse affect on your yearly electricity bills in comparison to the GeForce GTX 770.