Many avenues to great network performance, ethernet or optical, just one more variable. And then you have the variable as to how each is implemented. I've chosen optical as my preferred path, but optimization here includes running every FMC off lps, quality power cord into balanced transformer PC. The generic FMC can be bettered with Sonore optical, I'm also beginning to see optical enhanced devices from other companies.
Also, optimizing network both prior and after server is critical, anywhere noise has opportunity to enter and contaminate has to be isolated, and no switching power supplies.