The old Unika W300 used a 20W heat element. The heat element of the Unika+ was upgraded from a 20W element to a 30W element in Q1 2019.
The knife arm of the Unika+ was completely redesigned in December 2019 so that in extreme cases, the user can no longer bend it during use.
The aluminum (shiny silver) parts of the Unika+ have been significantly improved in quality since February 2020 in cooperation with a new supplier. See Troubleshooting 3.