In terms of overall gaming performance, the graphical capabilities of the Nvidia GeForce GT 755M are marginally better than the AMD Radeon R9 M365X 4GB.

The GeForce GT 755M has a 355 MHz higher core clock speed but 8 fewer Texture Mapping Units than the R9 M365X. The lower TMU count doesn't matter, though, as altogether the GeForce GT 755M manages to provide 6.4 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 GeForce GT 755M has a 355 MHz higher core clock speed than the R9 M365X and the same number of Render Output Units. This results in the GeForce GT 755M providing 5.7 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 GeForce GT 755M, 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 GeForce GT 755M.

The R9 M365X has 2048 MB more video memory than the GeForce GT 755M, so is likely to be much better at displaying game textures at higher resolutions. However, overall, the GeForce GT 755M has superior memory performance.

The GeForce GT 755M has 22.4 GB/sec greater memory bandwidth than the R9 M365X, which means that the memory performance of the GeForce GT 755M is slightly better than the R9 M365X.

The Radeon R9 M365X 4GB has 640 Shader Processing Units and the GeForce GT 755M has 384. However, the actual shader performance of the R9 M365X is 340 and the actual shader performance of the GeForce GT 755M is 376. The GeForce GT 755M having 36 better shader performance and an altogether better performance when taking into account other relevant data means that the GeForce GT 755M delivers a noticeably 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 GeForce GT 755M requires 50 Watts. The two GPUs require the same amount of wattage to run. As such, there is no need to worry about which will more significantly affect your yearly electricity bills.