Do you notice much difference in average speed between your bikes?
I notice a sensible raise in average number of drifts in winter.
Seriously, I take the same trip to work every day for 4 years. Tested it with many of my bikes. The profile is flat and tarmac quality is variable urban suburbs i.e. not as rough as open roads in back country. I have crossing lights and bike lanes stops to test my sprint aptitude as well as long rolling straight lines at the end, when warmed up.
The Allez Sprint is at home and even if I have no computer anymore (I'm over 40, it's my bike-to-work routine, I just have to keep up with the young roadies along the trip) I felt it very quickly. It's intended for that terrain.
Roubaix smoothness will takes over after much more km, less as the ground becomes rougher. Take it on rough terrain and add 90km and the Roubaix will be in front, without any doubt. I climbed and descent with a SuperSix Evo with Red blings on roads I know by heart : it was slightly easier to climb, sensibly faster on straight but rougher for the butt and back. The Roubaix was so much easy with descent curves with gravel and bumps at speed. At low speed I could recover from hammering session quickly with the Roubaix, with a better (upward) position and less fatigue by km.
I can keep the speed more easily on the Allez, even if it add some back pain, my legs will have to give less energy to maintain speed and get to a target speed. The upper body will take more pain though. On the otherside, freshly made tarmac mats will be less rewarding with a Roubaix.
Your average speed match the mood/ride/weather of the moment that eventually meets its horse. If your stable gives you more than no choice !