I think it is all in bike fit and tyre/wheel choice when it comes to comfort over long distance rides, not some geometry category.
For example, I am far more comfortable on long rides on my aggressive race bike than my friend on his endurance bike. This is because I went out of my way to find a great bike fitter to inform frame choice and swapped parts to dial in the dimensions to suit my limb proportions perfectly, instead of relying on a rushed post-sale bike fit in a shop. And I put on a modern wheel set with a wide internal and external width so the same 28mm tyres sit better and measure wider.
Based on this, the thought of adding some endurance bike to complement my race bike for 'longer rides', and then making some day to day decisions which to pick for a certain ride, is nonsense, as long as we are talking about rides that fit within a single day. For anything beyond that, it would really be more about mounting points for on-bike storage.