For those who can't tell much difference between 1080p and 4K, I bet you would with two screens side by side (not that you'd be in a position to try it).
It's more immediately obvious in static images and menus which is why it's 4K gaming (particularly with HDR) that has impressed me most. I know that doesn't appeal to many here though.
Pretty much every 40"+ TV on the market is 4K now but as with the early days of HD, few are taking full advantage of it. The extra to get Netflix in 4K may be worth it to you but I think Sky ask an extra £12 a month which is a bit rich. UHD Blu-ray will outperform both but who wants to buy movies on disc at £20 a pop these days?
Other than the above, you're viewing upscaled HD content. If your previous TV is getting on a bit, other technological improvements might mean the newer panel does a better job even with upscaling, but I found Sky's regular 1080i content looked a tad better on my old Pioneer plasma than my new Sony OLED. Native resolution is king there.
Anyway, not sure what my point is here. Enjoy the new telly!