I'm no triathlete, but the SuperSix and the CAAD10 are on my list of bikes to try. I'm not familiar with Cervelo or Scott (though it sounds like you're leaning toward the Cervelo or C'dales).

Cannondale's numbering system means that the lower the number, the nicer the components, even though the frame is the same. If you can afford it, go with the 3 rather than the 5. Are you looking at the women's version, or the unisex?

Go with the bike that feels best, with the nicest components you can afford.

Have you also looked at Trek and Specialized? Spec is expensive, but they're good for those of us with short torsos.