I haz both - the non series Di2 hydro and the new dura Ace Di2 hydro
New Di2 is great, the control over Garmin is really useful, and the brakes are better too. Hoods are fractionally shorter and more comfy. I’d upgrade if you have the funds and the option.
I have R785. I want the new stuff. I want someone who's used both to 'splain any diffs.