Regarding differences between the '19 and the '20. The video above outlines most of them. Of course, color changes.
In the video Matt says he does not think the vent button is important. Well, if you ride in the rain much, it can make a big difference.
I personally leave mine open all the time to reduce head buffeting, Except when it is raining hard, I do close it, otherwise it shoots a significant amount of water straight at my face. I would not want one that I could not close the vent on.
HD has come up with a new acronym for 2020, but the features are the same for the Tri-Glide in 2020 as 2019.
There's a full explanation/breakdown of the RDRS features on the HD website, that can be seen here-
https://www.harley-davidson.com/us/en/content/reflex-defensive-rider-systems.html
Regarding the "Advanced Braking", all 4 of the features on the 2020 are also standard on the 2019
Regarding the "Traction Control Systems" this was also standard on the 2019's
Regarding the "Drag Torque Slip Control" this was also standard on the 2019's
So they have a new acronym, but no different features than standard on the 2019 Trikes.
Oh, and there was a price drop in 2020.
If riding in the rain is not on the agenda, and if 2020 colors are appealing, then the future value of a 2020 is more than a 2019, otherwise, not much difference.
Kevin