I don't work in telly any more (Hurrah!) but here's my £0.02
All the gimmicks are to make you buy more crap when the manufacturer wants you to, rather than when the kit actually needs replacing.
Things you actually need:
1. Decent sound system.
However you happen to define decent, remember that you're mostly listening to the sound, not looking at the pictures. Trust me on this.
2. A screen whose resolution and size is correct for your viewing distance.
Numbers on this vary - THX standards are different from everyone else's - and there's quite a bit of leeway but it's relatively simple to work out the range, and these days there are online ready reckoners that do it for you. For 1080, the distance is further away than for UHD/4K(/8K - I mean, really?), because the limiting factor is the pixel size and distance at which you see individual pixels (Snellen limit). For most people the viewing distance is fixed by the size/layout of the room, so if you go to 4K for the same room you'd ideally want a bigger screen, and there isn't much overlap between recommended distances for the same size 1080/4K screen. My 46" 1080 screen is roughly 2.5m (about 8') away which is in the middle of the range for that size, but if I went to 4K it would need to be a 65" screen to be in that range.
3. Technology appropriate to the resolution and dynamic range of your screen
If you're streaming, and you go to 4K, you should probably think about the High Dynamic Range aspect too. Old-school telly was constrained in its parameters by the fact that CRT screens used phosphorescent coatings which glowed, and this kind of thing is notorious for non linearity. Much Maths. Many headscratch. The maths fudged things by shifting the electronic parameters of the capture side (gamma) so that when it was shown through the non linear screen it came out kind of correct, but it was never possible to reproduce reality from black to white, so the dynamic range was also constrained. This put limits on how things were lit, shot, and graded for viewing. The colorimetry was similarly constrained for different reasons, and there were such things as ‘illegal’ colours - colours in real life that couldn’t easily exist in telly in the PAL system in the UK. If you lived in the north west of England in the 90’s you could see illegal colours on TX of Star Trek TNG, where the blue of the credits went below sync level and used to disrupt the line sync.
Now we have a much-different set of screen parameters, and can show stuff we couldn’t previously transmit. Purple, for example.
In reality this creates more problems than it solves. If you’re watching old school transmitted telly, you need the correct gamma, as per the last 50+ years. If you want to see High Dynamic Range in your streaming service, you need a system that will decode HDR. The BBC were opting for Hybrid Log Gamma which is backwards compatible with the original gamma - if you have the right screen receiving HLG you can see the HDR, if you don’t you can see it as it used to look without the HDR making it wrong. All screens should do standard gamma, but there are options for HDR - standards are everything, and there are many - and the transfer function for some HDR systems isn’t backward compatible. HDR10 and its variations allow for the basics of HDR, and Dolby hope that everyone will eventually adopt Dolby Vision (because of course), and the world is full of buzzwords like ‘tone mapping’ and ‘REC.2020’ (see also: Rec.709, Rec.2100, Rec.1886) which I absolutely guarantee that almost nobody outside the industry (and very few within it) actually understands. Don’t start me on ACES colourspace, and whether a colour is actually a colour if humans can’t see it, I can bore for England on this stuff.
Find out what your streaming service supports, and get a screen that does at least that. If you know what standard they’re aiming for in the future it’s a bonus if you’re compatible with that too. HLG, HDR10 or HDR10+, Dolby Vision and PQ could all be shown if you’re looking for buzzwords or stickers on the kit. Of course, if you're not going to be paying for 4K/HDR then you don't need it, but if you might pay for it later you'll need the right screen.
4. Thinking of colorimetry, I would go with a screen whose parameters can be set correctly. At the very least make sure you can alter the main colour temperature of the screen to something other than 9300K, because that’s too blue, and most screens I dealt with in the last ten years came out of the box like that. 6500K is correct for the UK, and there should be a menu option to at least get you into that area, even if you don’t have the screen colour calibrated.
Otherwise, I’d go with whatever provides your service and fits your price bracket. If you want forward compatibility for the long term, get a monitor and a separate streaming box so you can change the technology without being subject to the screen manufacturer’s planned obsolescence.
As ever YMMV, caveat emptor, suck it and see...
