Difference between MCX314A-BCCT and BCBT

Hi,

I'm setting up a couple of ESX hosts running on Supermicro boards. I plan to connect them directly (back to back) with the aforementioned cards.

Excuse my ignorance, but what's the difference between MCX314A-BCCT and MCX314A-BCBT? All I can see is the former states 10GBase-X and the later 10/100/1000Base-T, i.e 10 Gigabit and 1 Gigabit, but both the spec PDFs say "Interoperable with 10/40GbE Ethernet switches" and "IEEE 802.3ba 40 Gigabit Ethernet".

Is it that one uses fiber and the other uses copper?

Any help will be gratefully received.

Thanks

W.