Pixel Rate
The GeForce GTX 780 Ti should be quite a bit (about 46%) more effective at AA than the Radeon R9 270, and should be able to handle higher resolutions more effectively. (explain)
GeForce GTX 780 Ti 42000 Mpixels/sec
Radeon R9 270 28800 Mpixels/sec
Difference: 13200 (46%)