Every Dura Ace component is nicer than the Ultegra version. Finish, weight, materials, etc. The electric function is a different issue and does not elevate an Ultegra group to the level of a Dura Ace group. Even though Ultegra is a downgrade from Dura Ace, there may be good reasons for someone to choose it. Maybe you need easier gearing or have some other issue. As mentioned above, the frame may influence your choice. If not designed for Di2, you may not want the kludge of external wiring, etc.