Which graphics card is better for capturing hd gameplay and playing hd games?

I am buying a new pc and have already bought an avertv hd dvr capture card and was wondering whether the 1GB DDR5 NVIDIA GeForce GTX 550 Ti [2 DVI, mini-HDMI. VGA adapter or the 1GB DDR5 Radeon HD 6850 [2 DVI, 2 mini-DP, HDMI. VGA adapter is better. Hp offers both for $200 and idk which is better.... I will have 9gb ram, 1.5tb hard drive, and an i7-2600 quad-core processor with Turbo-Boost [up to 3.8GHz, 8MB cache. And like I said 1080p gameplay plus game play capture and video editing. Thanks for any help!