I have to ration disk space and internet here is typically not amazing

I'm totally fine with something like 540p or 480p, although I guess that's because my preference is good ol' TV shows that aired in the 90s or 00s over TV cable, so I'm fine with SDTV quality. And honestly, there's not much sense in downloading all seasons of, say, Ally McBeal in 4K when you can download 8 full glorious 90s shows with their entire seasons in SDTV in the same space.

Even with "modern" stuff, I've seldom found a movie or TV show post 2012 that merits anything higher than 720p. I don't get why don't movie codecs get a multi-res options so that for example you can get the action scenes in 1080p, even 60fps if you want, but the melancholic scenes and the quiet drama scenes and the credits in 480p. Would save lots of space without losing quality where it matters.

I downscale movies and shows I download to 480p and transfer them to my modded 3dsxl cuz they look good enough for me and I can fit a lot of stuff on it!

Only when the artifacts in 4k look bad - like black squares on a black background due to compression. 1080p in that case is preferable.

I download everything in the best quality I can find and will sometimes replace it when there’s better quality available. I can afford storage and I don’t really care how long it takes to download as I have other stuff to watch/play anyways.

After like 5-10 years of ripping 4K Blu-rays without re-encoding, I just can’t go back. The only time I’ll go back to anything less is if the source material was shot in it.

If it is a cartoon, or even anime, I don't mind between 720p and 1080p in most cases, but that is just about that.

Maybe you're not noticing the difference between 720p to 1080p is due to the decoding used. The rips with a lower file size often get there by means of compression, and some uploaders (such as YIFY) heavily compress the videos to where I don't even notice much of a difference, however I'm going to assume you're not downloading the 3GB (average size for HQ) 1080p film.
Then again eyesight plays a role along with display.

I wouldn't bother with 4K usually, however once I upgraded to a 1440 monitor downscaling from 4K actually provides a fair bump in overall sharpness and detail (some films more than others), however the file size is usually over 10GB per film.

I have cheap tv and slow internet, so I am completely comfortable with 720P or 1080P (depends which streams faster). I am also and grew up with 420P, so that helps.

I prefer them as well but if I want to keep something I usually encode to 576p I still don't really see any difference on my displays and it's just something I've been doing since I first tried encoding for the Sony Vita.

I usually opt for 720p for movies and SD for shows. They're good enough for me and I can store way more. The other thing is the devices and screens are dated now so at some point in the future I'll probably want to get it all again at better quality but for now it does the job.

5mbps is high in my book, i used to download 1080p stuff and games on an adsl network and trust me I WISHED that shit could reach 5mbps ! Most of my pirate life i'd have miraculous spikes at 1mbps and i still always went for 1080p stuff or if I can't find it in that quality 720. To me when i watch something i want to enjoy it to the fullest so i don't even bother with lower quality, i don't have 4k hardware so i don't bother with that.

(I've enjoyed fiber connection for a year or two and i always get surprised by the speed of it lmao)

I cant say I care as much as I used to, since encoding has gotten quite good, but I have also gotten better at seeing (aka. worse at being distracted by) compression artifacts so while I am less of a perfect remux rip supremacist, I'm also more sensitive to bad encodes so its a double edged sword.

I still seek out the highest quality versions of things that I personally care about, but I don't seek those out for absolutely everything like I used to. I recently saved 12TB running a slight compression pass on my non-4k movie library, turning (for example) a 30gb 1080p Bluray Remux into a 20gb H265 high bitrate encode, which made more room for more full fat 4K bluray files for things I care about, and the few 1080p full remuxes I want to keep for rarities and things that arent as good from the 4k releases or the ones where the 4k release was drastically different (like the LOTR 4k's having poor dynamic range and the colours being changed for the Matrix etc), which I may encode in the future to save more space again. I know I can compress an 80gb UHD bluray file down to 60gb with zero noticeable loss, thats as far as I need to go, I don't need to go down to 10gigs like some release groups try to do, and at that level of compression you might as well be at 1080p.

I cant go as low as a low bitrate 720p movie these days as I'm very close to a large screen so they tend to look quite poor, soft edges, banded gradients, motion artifacts, poor sound etc. but if I were on a smaller screen or watching movies on a phone like I used to, I probably wouldn't care as much.

Another side to my choice to compress is that I have about 10 active Plex clients at the moment and previously they were mostly getting transcoded feeds (mostly from remux sources) but now most of them are getting a better quality encode (slow CPU encode VS fast GPU stream) direct to their screens, so while I've compressed a decent chunk of the library, my clients are getting better quality feeds from it.

@VitabytesDev

You aren't alone. I prefer 360 or 480 p
Because:

1. It's faster and not much difference I still get the content/knowledge
2. It reduces my carbon footprint

I don't have that much hard drive space to keep the giant high quality files and there are some shows that it's pointless. Why would I watch a 1080p version of something filmed on video for example

Where do you live that only has 5mbps? It must be somewhere really remote.