The Synapse and the SuperSix are quite different bikes.
Until this year (when they used Cyclocross bikes "re-purposed" for the event) the Liquigas-Cannondale team used the Synapse for Paris-Roubaix, it's oriented toward the comfort end of the spectrum, is more upright and shorter than the more aggressive design of the SuperSix.
It depends what kind of riding you will do with the bike, well worth taking both out for a good test ride over mixed terrain to see which suits you.
The Synapse and the SuperSix are quite different bikes.
Until this year (when they used Cyclocross bikes "re-purposed" for the event) the Liquigas-Cannondale team used the Synapse for Paris-Roubaix, it's oriented toward the comfort end of the spectrum, is more upright and shorter than the more aggressive design of the SuperSix.
It depends what kind of riding you will do with the bike, well worth taking both out for a good test ride over mixed terrain to see which suits you.