Exactly what it says.
I'm thinking of going for one of these and I'm deciding whether or not the Carbon is worth the jump in price.

How much lighter will the carbon six be?
geometry differences?
spec differences?
handing differences?
comfort over long distances (i want to ride a couple centuries a year)?

I tested the CAAD9 in the LBS and liked it very much. But they don't have a Six to test out.

I thank you in advance for any light you can shed on this situation.