The guy who check this says even if it is set to uber mode still amd is 13% slower than the 780ti.But if we overclock 780ti its pretty sure it would be better than R9 290x in uber mode.Only in 4k they perform quiet similar
"According to the official data NVIDIA GeForce GTX 780 Ti would perform 30% better than 290X. Of course we are looking at the numbers from NVIDIA, so it’s necessary to take these numbers with a grain of salt. I was told that in ‘real’ benchmarks GeForce GTX 780 Ti is about 20% faster than 290X in Quiet Mode. In Uber Mode R9 290X is still slower than 780 Ti, but only by 13%. If we add 4k benchmarks this number will get even better in AMD favor."
Read the source guys.