After reading all the comments I’m thinking it really comes to what you’re able to see. If you see no difference between 60 and 120, good for you, set it to 60 and save some battery. If you’re able to see the difference, like I do, you’ll just enjoy the extra smoothness. I’ve always seen the difference between 60 and 90/120. I think it also comes to the content. For me it’s like this:

• For videos, whatever refresh rate is ok as long as that was the intent of whoever created it.
• For games 30 is playable, 60 is good, 120 is beautifully smooth. The type of game will also play a role here. An fps will benefit more from higher refresh rates.
• For moving UI elements 30 is unusable, 60 is ok, 120 is really comfortable.

TL;DR Some people will see it, some people won’t. Do whatever works best for you.