It will be a question of the motherboard cost (X99 vs X370), the electricity cost (160W Xeon vs 95W Ryzen), and what you want to do with it. You get more cores and more memory bandwidth with the Xeon but they aren't overclock friendly. To take advantage of the memory bandwidth, you have to buy 4 DIMMs. You get more PCIe lanes from the CPU. But if you aren't running SLI it doesn't matter.
There is no "right" answer.