Top performing processor for X58 chipset-based boards is Core i7-990X.
Do you mean IF overclocked?
Because overwise I can't see how the I7 is better. 'Tied' and 'close' is what I would use to describe it, but not better.
Also has slightly less Max Mem Bandwidth, no ECC support and lacking couple of extensions.
What's more, price for a used 990X is double compared to the other two Xeon CPUs. And given the fact (on paper at least) their identical performance (no overclocking) it makes no sense to even consider it as an option.