Hey,
For gaming, the single 5960X will show better results. Due to its higher Single Core performance, and the fact that games cannot utilize anywhere near the amount of cores that the Dual-Xeons have. The 5960X can also be easily overclocked, giving it a larger advantage.
But for your game design work, if it is a very CPU intensive workload, then the dual Xeons will show much better performance than the 5960X.
A possible option could be to get 2x Six Core Xeons, as they have a higher single core performance than the 8 core one you posted, they would perform better in games. But still having a massive 12 Cores - 24 Threads for your game design Workload.