I have no idea why, but it seems that most of these reviewers that are using high and no AA benchmarking settings have the 780Ti thrashing the 290X and it all seems strange.
maybe the 780Ti does thrash the 290x on lower settings i don't know, i never tried low settings on either, but if i'm buying a Top end card, i expect to run my games with max settings, i don't fancy having the "Fastest card in the world....at lower settings".
I had both the 780Ti and 290X just before xmas, i tested both on BF4 and other games, i'm not biased, both cards offer incredible performance but i noted that the 780Ti's build quality and easy of use was nothing short of amazing.
I loved the 780Ti, it's a fantastic card with killer looks, awesome cooling even in Ref form and is very quiet, but it's performance isn't any better than a 290X in BF4, infact the 290X was slightly faster and that was before Mantle.