If you want to compare bike to bike it would be Ruby vs. Synapse. Is the System Six Aluminum with Carbon fork and post? I can't remember. I don't have either bike but I am biased to Cannondale, I ride a Synapse and DH a R5000. How do the components compare? Fit? What are you trying to accomplish, race, centuries?
Amanda
2011 Specialized Epic Comp 29er | Specialized Phenom | "Marie Laveau"
2007 Cannondale Synapse Carbon Road | Selle Italia Lady Gel Flow | "Miranda"
You don't have to be great to get started, but you do have to get started to be great. -Lee J. Colan