Those are all very nice bikes. The Domane and Synapse are endurance bikes and will have a more relaxed geometry and may be more comfortable. The CAAD 12 is also a great bike but it has more traditional geometry with a horizontal top tube. I recommend you test ride lots of bikes to compare.

One piece of advice..... tire pressure can make a big difference in how a bike feels. I test rode a bike that had over inflated tires and I could feel every little bump in the crappy road. Wider tires with lower pressure will give a smoother ride. Make sure the tires are inflated properly on bikes you test ride.