I am not too sure Muireen. I'm in bed and my notes are downstairs. Would have to look it up as I can't recall the things on synapse and caad.... but i think it had to do with tires. We'd probably take those narrower than the 35 they come with. We don't intend to ride on mud, nor mountains, etc... it would be better than our current old hybrids for 100km rides through a mix of gravel and asphalt.
Also, my husband was really impressed on how light both cannondale were for the type of bike.