I game on my PC at 4k/60 with HDR and I can tell you, there is a good difference between 1440p and 4k. I only use a 55inch TV and I can tell night and day the difference. Just like I could tell the difference between 900p and 1080p.
Once you start getting use to a resolution, you can tell when it changes. Once you get use to 4k, you can tell when you play a game that isn't in 4k.
I am not saying 1440p or 1080p are bad resolutions however compared to 4k, there is a eye popping difference.
What about dynamic resolution? Can you tell when a game drops resolution during explosions and stuffs?