[noggin]

Also, since you mention BT2020, I assume you're interested in HDR content. In which case, you want to avoid LibreELEC, as it doesn't support HDR period from what I can tell. The Vero does, and there are one or two Vero reps lurking around here to help answer questions which is always a plus, but the fatal flaw (IMO) is that they do not support Netflix or Prime Video without having to go way out of your way. If you want Netflix and/or Prime Video, the Shield is probably still the best option there is right now. 

Some LibreElec/CoreElec builds for some platforms - like the AMLogic S912/S905X platforms (e.g. Minix U9-H) do support HDR10 10-bit output (some kernels seem to add 10->8->10 bit dithering though) and there can be issues with the correct metadata for average and peak light levels being correctly passed AIUI? And as you say the Vero 4K (S905X) and Vero 4K+ (S905D) handle it in OSMC.    

Thanks for the additional clarification. It makes my choice a bit easier to go with the Vero 4K+. Is there any performance improvement between the Vero 4K and 4k+ as well or is the S905X and S905D pretty much the same?   

The main difference, AIUI, is the the Vero 4K+ has Gigabit Ethernet, whilst the Vero 4K has 100Mbs Ethernet and for high bitrate UHD Blu-ray rips you really need something better than 100Mbs.  

If you already have a Vero 4K you can use an extenal USB 3->GigE adaptor in a USB 2.0 port which, whilst not providing full GigE speed, will give you speeds fast enough for the demanding UHD Blu-ray rips.  If buying from new, I'd seriously consider the 4K+ if you want to play UHD BD rips.

AIUI there is no video quality difference between the two models.