I was in my local Apple store last night and there was a 2017 nTB 13" displayed right next to a 2018 TB 13", so I got to play with both of them back and forth. On each, I loaded Safari and Pages and MS Word and a few other oddball programs, like Calendar and Maps, etc. And let me tell you, the speed difference between the two was minimal--both computers were incredibly snappy, programs loaded near instantly. The 2018 was definitely faster, mind you, but for everyday use, it was hardly noticeable; the 2017 easily kept up with the 2018.
But I get it, if you're doing something power-hungry that requires four cores, ok, the 2018 wins. But if you're just Joe Bob nobody like me, and all you're doing is word processing and surfing the web and even Photoshop work, I think the 2017 is absolutely fine. Or even the 2016.
I will say this, I did definitely notice the effect True Tone has on the display quality. The whites on the 2017 display were slightly blue, but on the 2018 the whites were as white as my butt. Seriously, there was a big difference in the hue of each respective display, but in the Apple store, they've got big fluorescents all over the roof, and I think that's where True Tone really shines. At home, there may be no discernible difference at all. My ten cents.