SoSmellyAir

Sounds like you are partial to the Specialized brand and just named its carbon fiber road bikes (except the e-bike). Geometry-wise, one of these is not like the others. The Roubaix is an endurance bike while the Tarmac and Aethos have a more race bike geometry (lower stack height, more reach) that requires the rider to bend more and keep his/her torso more parallel to the top tube. So while it makes sense to cross-shop the Tarmac and the Aethos, it is rare to cross-shop all three of these bikes, at least when buying a first road bike. Best to get a test fit and test ride to see which type of geometry you prefer.