In terms of overall gaming performance, the graphical capabilities of the Nvidia GeForce GTX 860M 2GB SLI are massively better than the AMD Radeon HD 8850M.

The GTX 860M has a 404 MHz higher core clock speed and 40 more Texture Mapping Units than the Radeon HD 8850M. This results in the GTX 860M providing 57.3 GTexel/s better texturing performance. This still holds weight but shader performance is generally more relevant, particularly since both of these GPUs support at least DirectX 10.

The GTX 860M has a 404 MHz higher core clock speed and 16 more Render Output Units than the Radeon HD 8850M. This results in the GTX 860M providing 22.9 GPixel/s better pixeling performance. However, both GPUs support DirectX 9 or above, and pixeling performance is only really relevant when comparing older cards.

The GTX 860M was released less than a year after the Radeon HD 8850M, and so they are likely to have similar driver support for optimizing performance when running the latest games.

The GTX 860M has 2048 MB more video memory than the Radeon HD 8850M, so is likely to be much better at displaying game textures at higher resolutions. This is supported by the fact that the GTX 860M also has superior memory performance overall.

The GTX 860M has 128.4 GB/sec greater memory bandwidth than the Radeon HD 8850M, which means that the memory performance of the GTX 860M is massively better than the Radeon HD 8850M.

The GeForce GTX 860M 2GB SLI has 1280 Shader Processing Units and the Radeon HD 8850M has 640. However, the actual shader performance of the GTX 860M is 1896 and the actual shader performance of the Radeon HD 8850M is 496. The GTX 860M having 1400 better shader performance and an altogether better performance when taking into account other relevant data means that the GTX 860M delivers a massively smoother and more efficient experience when processing graphical data than the Radeon HD 8850M.

The GeForce GTX 860M 2GB SLI requires 120 Watts to run and the Radeon HD 8850M requires 45 Watts. The GTX 860M requires 75 Watts more than the Radeon HD 8850M to run. The difference is significant enough that the GTX 860M may have an adverse affect on your yearly electricity bills in comparison to the Radeon HD 8850M.