Keep in mind, the larger frame will have a taller head tube. Several shops told me with my fitness level at the time, if I wanted a more relaxed geometry, if I were able to ride two different sizes well, choose the larger of the two. YMMV. Glad you're working through your options.
The rough ride was my concern when you said CAAD8, thus my suggestion of trying to get the Synapse. One think I'd look into is tire size. I'd guess it has 23's on it now. Will 25's fit? If so, that will soften the ride up a touch. I have no desire to go back to 23's.