That is a good question.
When I got it, it came iwth the plain case back, only.
Then, 2 years after, or 3, I don't remember well, it came with the display case back.
I was wondering which one I preferred, and tested both of them, acoustically speaking, to know if there would be more than an aesthetical reason to my choice.
1st, I can tell you that I much prefer the sound on my " Sonata 1 " than on the " Sonata Cahedral ", the sound on mine being rounder, suaver, to my ear and taste.
2d, I am not a fan of the " Display Back cause ".
I mean, when there is something exceptional or interesting to see, ok, the case back has an interest, and is not only a " Trend Thing ".
But on the Sonata, the interest and the aesthetic of the movement is limited to me.
Best,
Nicolas.