For Multi-threaded software, which encompasses most rendering packages, etc... You'll typically see better performance with the core count on the 8350. For single threaded operations, the 4670K would prove to be much better.
But...If you're adding in gaming, the 4670K would be the best choice of the 2. It'll still crank out good speeds on the rendering tasks, but the gaming part would be far, far better. Where the gain on the 8350 on rendering wouldn't be as much as the gaming gain on the 4670K.
Recently went from an OC'd 8150 (4.0 GHz) to a 4690K for an ITX build. The performance increase surprised me.