How does BER compare between different 10GbE physical media?
Twinax is rated at 10^-17 at <= 10M
Fiber is generally 10^-18 or better (lot of variables here, though - especially on long haul)
Ethernet's minimum specification is 10^-12. This is where the contention comes in as far as FC goes - it may be that a TP infrastructure can support better than 10^-12 (and hopefully most do) but at 10G speeds even that much error translates to a bad packet every few minutes.