It depends on the person, really. I found the difference HUGE. I mean, clearer textures, better text, better colours all thanks to those extra pixels. 2k or 1.5k to be more precise, in my opinion, is worth it 100%.
The thing with your case though is that you want to have a portable monitor, it depends on what you mean by portable, but I don't think that anything above 27" is easily portable. And to be honest, PS4 PRO + 27" ain't the best combination.