The conclusion is much more clearcut this time compared to the other two frametime tests we did. Based on the render times of individual frames, the Nvidia GeForce GTX 660 is most definitely better than the AMD Radeon HD 7870 GHz Edition. In Assassin's Creed 3 the GTX 660 is faster, and the game is playable on its highest settings with Nvidia's card, something that can't be said of AMD's card. In Far Cry 3 the Nvidia card has much more stable render times, while the AMD card experiences peaks. It's the same story with Hitman: Absolution, consistent times for Nvidia, lots of variation for AMD. In Battlefield 3 and Max Payne 3 the two cards perform equally well.
So if you're looking for a graphics card in this price range, then the GTX 660 is the better choice.