The i7-5960x should win in both gaming, and rendering. Both of the cpus are handpicked, the i7 to be the best overclocking one, and the xeon to be the most reliable. So the xeon is better for server task since its more reliable than the i7-5960x. i7-5960x wins in very other aspect
They both have 8 cores and 16 logical cores.
They both have 20MB L3 cache
But the i7 has overclocking possibility, and already a higher clockspeed to begin with. So I do not know how a 8 core xeon would beat in any other manner than being more reliable. You have to keep in mind that the i7 extreme is also handpicked to be reliable and most potential to overlock.
I would go with the i7-5960x especially if you are gaming and using it for your other personal matters too. The i7-5960x is just better. Hope this helped you in deciding.
And you dont really need ECC 128gb ram solution unless you're doing some heavy server stuff. Besides if you are doing server stuff you should get a dedicated pc for it anyways. For that you should buy a xeon and get the ECC ram. For gaming and rendering 100% go with i7-5960x
ps. I would go with the i7-5960x in instant.