I switches from the Jr to the Sr. back in the spring of this year.
The first non-sound related thing that is better is that the upgrades to new firmware versions is so much better. The Jr was a PITA, while the Sr. just works every time, without a hitch.
For the sound related differences, I’m using RCA cables to connect the DSD to my pre-amp (Anthem AVM-60) and noticed that the sound-stage was better (wider, deeper, higher) than the Jr.