Originally Posted by
ZHVelo
The biggest factor for this is that the main reason endurance bikes are marketed as endurance is a more upright sitting position, but that that does not necessarily imply more comfort. After I got a fit on my aero bike, I became even more comfortable. The fit made my position more aggressive, not more upright.
By comfort, I was thinking more of ride compliance, although with wider, higher volume tyres it's maybe less of an issue than it used to be. All the same, if you compare bikes across a single brand (Canyon in this case), their endurance model will have the most compliant ride. In this case the Endurace with skinny seatstays, split seatpost, tapered seat-tube, wider rims, compliant bars etc. The Ultimate is going to be next best (in terms of ride comfort) - differences being a standard non-split seatpost (which is interchangeable with the split version), narrower (but still quite wide) rims, stiffer bars etc. But it's a very similar frame. Then finally the Aeroroad is going to lose a bit more ride comfort again with aero seatpost etc. This is their most focused race bike outside of Alpine climbs or TTs.
Whether any of this matters depends on the use case and rider. But it is worth mentioning and largely explains why these different bikes even exist in parallel. I find it interesting watching the Grand Tours and seeing some riders on the Ultimate and others on the Aeroroad on the same road stage. For me that says there isn't much in it overall and it largely comes down to personal preferences and trade-offs between aero/weight/ride comfort.