The CAAD 10 is the sportiest and you will feel that in the riding position and the ride.

The Synapse Alloy and Secteur will have compact geometry and comfort oriented rides. Neither will match the comfort of their CF counterparts but unless you are routinely cruising at 18+ mph on rough pavement it won't be an issue.

No, the comfort level and riding position of each bike will not affect its performance at all.

I do believe the Synapse alloy have a semi-compact geometry while the Specialized Secteur has a full on comapct geomentry. You will notice that in their riding position with the Specialized having a more upright, more comfortable position even down in the drops. Either of these bikes will be very close. I believe the Cannondale has a slight advantage in component group and price. If so, the Cannondale Synapse alloy is the better value.