The GT 750M has a 216 MHz higher core clock speed but 8 fewer Texture Mapping Units than the R9 M370X. The lower TMU count doesn't matter, though, as altogether the GT 750M manages to provide 1.1 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 GT 750M has a 216 MHz higher core clock speed than the R9 M370X and the same number of Render Output Units. This results in the GT 750M providing 3.5 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 M370X was released over a year more recently than the GT 750M, and so the R9 M370X is likely to have better driver support, meaning it will be more optimized for running the latest games.