[User 309201]

So besides the apple and amazon specific nature of each device, would it be fair to say that from a performance and video / audio decoding perspective, the ATV 4K 2021 and the AFTV Cube S922Z are pretty much identical?

Well, you can't run Kodi on an Apple device, as far as I'm aware. There are somewhat similar apps, e.g.MrMC (which is a distant Kodi relative) or Infuse, but they don't support Kodi add-ons.

The Cube has some weird deficiencies - it can't seem to decode VC-1 in hardware, and gives me what look like deinterlacing errors in Disney Plus(!). Also its native apps mostly don't support refresh-rate or resolution switching. (Prime Video does support refresh rate changes, but that's about all. There are some third party apps that handle it - Kodi, of course, and Smart Tube Next for YouTube.)

The Cube also can't handle 24Hz playback. It can handle 23.976Hz, but not 24.000Hz, which is a problem for Netflix movies.

I can't remember if Infuse supports pass-through of Dolby TrueHD on Apple; the Cube definitely doesn't support that in any app. It's quite possible the Apple can't do it either.

I don't think the Apple supports HDR on YouTube. It definitely doesn't support subtitles on BBC iPlayer and can't do 4K playback on iPlayer either. The Cube can do 4K playback on iPlayer, but not in HLG HDR and only at 59.94Hz, not 50, so that's pretty useless too.