See, I knew I would look stupid!TC - theatrical cut
DC - director's cut. 4K disc is just TC. DC only on 1080p BD and streaming.
If you want the best picture quality in motion stick with MA. Not for all films but for select films only.
Lionsgate and Paramount don't do MA.
Sony films on MA are 4K HDR10 5.1. So if you prefer DV DA then stick with iTunes counterpart of Sony films. If the movie won't benefit from DA or if you want the best picture then stick with MA.
Thanks for the MA/iTunes comparison...I will try some movies out on both, and see how they compare.