According to this screenshot of TessMark scores (from AnandTech), the GeForce GTX Titan is around 50% faster than the GTX 680 in tessellation.
Unsurprisingly, Titan is well ahead of anything else NVIDIA produces. At 49% faster it’s just a bit over the 46% theoretical performance improvement we would expect from the increased number of Polymorph Engines the extra 6 SMXes bring. Interestingly, as fast as GTX 580’s tessellation performance was, these results would indicate that Titan offers more than a generational jump in tessellation performance, nearly tripling GTX 580’s tessellation performance. Though at this time it’s not at all clear over just what such tessellation performance is good for, as we seem to be reaching increasingly ridiculous levels.
The Tech Report has some results with TessMark too:
The last couple generations of Nvidia GPU architectures have been able to sustain much higher levels of polygon rasterization and throughput than the competing Radeons. The big Kepler continues that tradition, easily leading the GeForce GTX 680, even though its peak theoretical rasterization rate isn’t much higher. Most likely, the GK110’s larger L2 cache and higher memory bandwidth should be credited for that outcome.