3DMark
3DMark is the latest version of this hugely-popular synthetic benchmark. Making use of DX11 features such as tessellation, compute shaders and multi-threading, it provides modern-day results and is available as a free download.
Here we go. AMD's Radeon R9 280X's gets slapped down by the new bad boy on the block. The R9 290X's visceral muscle makes it substantially faster; even putting the GeForce GTX Titan in the shade. If we're comparing like-for-like products on a financial basis, the R9 290X is way ahead of the GTX 780.