The 4790k is better than the xeon in terms of performance. The 4790k is overclockable while the xeon is not. You do need a better mobo than the one included to overclock the i7 though, which would cost more, and the gains from oc even in gaming isn't much to justify the cost.
If you're going to go down the road of xeon, the xeon e3 1231 v3 represents a much better value for the money.It's basically a locked multiplier i7 4770 without the integrated graphics. And since you're not overclocking the xeon, you can pair it with a cheap reliable mobo like the gigabyte b85m-d3h. The mobo will not affect performance. Plus you can save money by using the better variant included stock cooler in the cpu box.