4k does make a difference if you are reading text, or doing coding.
I have a Macbook with retina at home and a ThinkPad without one at work. Yeah, retina makes text a little nicer, but overall it's not so big deal for me. It may be because, when I'm coding at work, I'm usually pissed off by a couple different things at least, so a less than perfect font is not even on my radar.
You're also closer to a laptop screen. After using a 14" 1080p laptop I definitely would never go lower than 1440p at that size again.