^+1. There's not enough performance difference between the GTX780Ti/780 and R9 290X/R9 290 to justify the increased cost, at least in most peoples view.
Pretty well all the better tech review sites compare plenty of cards as a matter of course during their reviews. Apart from our beloved Toms also look at: Tweaktown, Guru3D, Techpowerup and Hardwarecanucks...Amongst MANY, many others. 😉
The actual benchmark numbers will vary, each site uses a different rig for its tests and in some cases they have to run custom benchmarks because the game/s in question lack a built in benchmark tool so expect some variations.
Either card will run dual 1080 screens well but I'd opt for the R9 290 for its larger memory-the MSI Lightning or Sapphire Tri-X are both cool and quiet, but VERY large.
Nvidia brings PhysX and CUDA while Shadowplay allows you to record your gaming sessions in high def with little slowdown. Until there's a little more certainty about G-sync and how it will be implemented I'll not pass any comments on how useful this future feature may be, I'm certainly not going to swap my current card AND monitor to use it, besides AMD have their own similar tech under development.
Because the GTX780 produces less heat than the R9 290 cooling it is easier, so they run cool and quiet without needing a 12" cooler so one should be easier to find if the current case can't handle the massive R9 290 coolers.