This goes on a game-by-game basis and the same is true for AMD. For example Shadow of Mordor is known to be more optimized for AMD cards, and both Far Cry Primal and the new Hitman game definitely look like they run better on AMD cards, either because of optimization or because of DX12's Async Compute feature which only AMD cards benefit from at the moment.
Current nVidia cards are still good but taking into consideration several factors including DX12's Async Compute and the fact that nVidia has purposely tanked the performance of older cards in some instances to promote their newer ones, I cannot recommend getting an nVidia card if you expect any kind of future-proofing.
Finally, no matter how "optimized" a game is towards nVidia, the R7 370 will perform better than the 750 Ti.