Well just compared Revenant HDR on FandangoNow and MA. MA looked and sounded noticeably better (higher bit rate on video, and DD+ seemed a bit more robust than Fandango which is possible given the wide range of data rates allowed under DD+).
HDMI Gone Wild - Audio HDMI Chains: (min. upmixed Atmos) Sony X700(Vudu, etc.)
Oppo UDP-203-->LG OLED65B7 and SamsungK950 (4K Atmos discs and files + 2 more subs!)
XboxOneS-->K950 (DTS discs, 2K files, Fandango 2K DTSHD)
ATV4K-->AVRkey-->XboxOneS-->K950 (iTunes and Vudu atmos, &Infuse - dd5.1)
Roku Premiere+-->Oppo UDP-203-->K950(Fandango and MA HDR, DD+)