I don't think 100,000 can ever be less than 25,000 ; ) so I can't take that as much orthodox or even valuable, I'd dare to say, I'm sorry : ) Extra resolution or 4K for the sake of it will always give you a better cinematic whatever adjective we want to. The point is 75,000 can be not necessary if you only need 25,000 for : P or the extra 75,000 might be more demanding. Reckless argument when even wedding filmmakers or consumers are adopting such standard. Not necessarily mandatory though when by then, you may need to apply something you're not willing to, as for instance, because of a different workflow of your own or sharpness per se to end in acuteness unwanted (you can add blur @post anyhow) and not in your plans or needs into a specific project or sort of work, style/aesthetics and so on.
Without mention, from larger you can always go narrower, but not the opposite, so there's nothing 1080p is able to become that 4K acquisition or 4K -> 1080p cannot.
This reminds me the peregrine idea that digital can't show grain or mimic film stock when comes acquired in bits and bytes... *cough* *cough*
E :-)