I'm confident.
Radeon 7970 GHz ed. has 384-bit and 288GB/s memory bandwidth.
GTX 680 has has 256-bit and 192.2GB/s memory bandwidth.
You can clearly see that the 7970 has about 33% better bandwidth which means a lot on high resolutions. Take it with a grain of salt, because the two GPUs doesn't use the same architecture which means that the performance difference might be slightly different.
If adaptive vsync, PhysX, Cuda and TXAA is important to you, then go with the GTX 680. If not, then Radeon 7970 GHZ ed. will be better.