Unfortunately, that's not how digital streamers work. If a streamer supports a codec, the PQ will be 10/10 and if it doesn't, it won't even work. This is not analogue signal where the component quality matters much.
1.
Firestick 4k: It will play basic stuff. As I mentioned above, it won't bitstream HD audio (DTS, Dolby TrueHD), frame rate matching doesn't work very well, doesn't have ethernet.
As a firestick 4k user, I'd rate it 5/10 on features. It's a frustrating exercise in getting it to work on stuff.
2.
Shield: Will play basically everything you throw at it. A couple of things to note:
- It still runs android TV. So if an android TV app is badly coded or changes behaviour or doesn't expose metadata properly, it won't be able to do anything. For example, Netflix won't work with the auto refresh-rate matching as in the app it constantly changes refresh rates. You'll have to manually do that. Though this is a Google problem and android TV 12 is reportedly fixing it.
- ExoPlayer via Plex won't work with SSA/ASS subtitles. So any alpha based subtitles streamed via Plex for example will need to be transcoded. Though you can use Kodi/VLC to fix it as those players support alpha based subtitles.
- Not available officially in India. So you'll have to pay more + no warranty.
I'd rate it 9.5/10
3.
Apple TV 4k: The best streaming box, hands down. However, it has a couple of things missing v/s shield for local playback.
- It won't play HD audio like TrueHD/DTS-HD.
- It won't play Dolby Vision profile 7 (dual layer)
- No custom upscaling support like the shield. Shield has its AI upscaling which is based on Lanczos. Apple is using very basic upscaling and it doesn't support resolution matching (so will always output at one resolution unless manually changed).
I'd rate it 10/10 for streaming, 8/10 for local playback.
4.
Blu-ray players: If you want to play Blu-Rays, I guess you can get them. Not sure why you'd compare them to streamers. If you don't plan to play physical media, no point getting one really.
If you want the utmost highest quality PQ for local media, nothing even comes remotely close to MadVR on PC. You can literally customize it how you want and run it via an HTPC. It's really expensive with the current GPU shortage though. One with an RTX 3060 now will cost around 1 lakh, and you need around 3060ti for the max options.