http://gpuboss.com/gpus/GeForce-GTX-TITAN-BLACK-vs-EVGA-GeForce-GTX-780-Ti <--- GPU boss comparison
I would get the EVGA GeForce GTX 780 Ti because it has better clock speed and and other things and it is tones cheaper it may not have 6gb of video memory but that's not even necessary really 3gb is plenty even if you are dual monitor gaming with battlefield 4 for example.
Hope this helps - xXDahChubChubXx