In terms of overall gaming performance, the graphical capabilities of the AMD Radeon R9 M290X Crossfire are massively better than the AMD Radeon R9 M365X 4GB.

The R9 M290X has a 225 MHz higher core clock speed and 120 more Texture Mapping Units than the R9 M365X. This results in the R9 M290X providing 111 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 R9 M290X has a 225 MHz higher core clock speed and 48 more Render Output Units than the R9 M365X. This results in the R9 M290X providing 44.4 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 R9 M365X was released over a year more recently than the R9 M290X, and so the R9 M365X is likely to have better driver support, meaning it will be more optimized for running the latest games when compared to the R9 M290X.

The Radeon R9 M365X 4GB and the Radeon R9 M290X Crossfire have the same amount of video memory, but are likely to provide slightly different experiences when displaying game textures at high resolutions.

The R9 M290X has 243.2 GB/sec greater memory bandwidth than the R9 M365X, which means that the memory performance of the R9 M290X is massively better than the R9 M365X.

The Radeon R9 M365X 4GB has 640 Shader Processing Units and the Radeon R9 M290X Crossfire has 2560. However, the actual shader performance of the R9 M365X is 340 and the actual shader performance of the R9 M290X is 1958. The R9 M290X having 1618 better shader performance and an altogether better performance when taking into account other relevant data means that the R9 M290X delivers a massively smoother and more efficient experience when processing graphical data than the R9 M365X.

The Radeon R9 M365X 4GB requires 50 Watts to run and the Radeon R9 M290X Crossfire requires 200 Watts. The R9 M290X requires 150 Watts more than the R9 M365X to run. The difference is significant enough that the R9 M290X may have an adverse affect on your yearly electricity bills in comparison to the R9 M365X.