Unless you gotta have a bike like right now, why not wait for the end of season sales.
They are going to be some awesome deals this year.
Look, a brand new Cannondale CAAD 10 3 Ultegra is going for $2,270
CAAD10 3 Ultegra - CAAD10 - Elite Race - ROAD - BIKES - 2014
That thing could easily be had for $1,800 from shop caught with it.
This spring, Cannondale itself had a spring discount on the highend EVOs, starting at a thousand dollars:
Supersix Evo Spring Sale
There is so much new stuff that just came out like wheels and component groups, and there is even more new things coming, I think there will be a huge dumping of inventory this fall.
If the two you posted are what you are limited to, I would go with the Cannondale for cheaper.
That Cervelo is butt ugly and for me, over priced for what you're getting.
These reviews put it at $2,800, but the component mix could be the difference:
Cervelo S2 Road Bike Reviews - RoadbikeReview.com
I read somewhere about the harsh ride of the old S2, maybe someone here who actually rode one can help you with
what it is like to ride.
Be patient and good deals on new will be out there.