In terms of overall gaming performance, the graphical capabilities of the Nvidia GeForce GTX 980MX 8GB are significantly better than the AMD Radeon R9 M395X 4GB.

The GTX 980MX has a 315 MHz higher core clock speed but 24 fewer Texture Mapping Units than the R9 M395X. The lower TMU count doesn't matter, though, as altogether the GTX 980MX manages to provide 15.5 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 980MX has a 315 MHz higher core clock speed and 32 more Render Output Units than the R9 M395X. This results in the GTX 980MX providing 43.3 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 980MX was released less than a year after the R9 M395X, 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 980MX has 4096 MB more video memory than the R9 M395X, so is likely to be much better at displaying game textures at higher resolutions. This is supported by the fact that the GTX 980MX also has superior memory performance overall.

The GTX 980MX has 0.4 GB/sec greater memory bandwidth than the R9 M395X, which means that the memory performance of the GTX 980MX is marginally better than the R9 M395X.

The GeForce GTX 980MX 8GB has 1664 Shader Processing Units and the Radeon R9 M395X 4GB has 2048. However, the actual shader performance of the GTX 980MX is 2534 and the actual shader performance of the R9 M395X is 1259. The GTX 980MX having 1275 better shader performance and an altogether better performance when taking into account other relevant data means that the GTX 980MX delivers a significantly smoother and more efficient experience when processing graphical data than the R9 M395X.

The GeForce GTX 980MX 8GB requires 122 Watts to run and the Radeon R9 M395X 4GB requires 125 Watts. The R9 M395X requires 3 Watts more than the GTX 980MX to run. The difference is not significant enough for the R9 M395X to have a noticeably larger impact on your yearly electricity bills than the GTX 980MX.