[montroser]

I made a diagram of the way I think about it here: https://plectica.com/m/ADUNN80H4

When you map it out like this, the answer seems obvious that the place to invest your time is in learning the standards.

[exodust]

Jquery selectors are still more powerful, even if vanilla is faster.

There's more options, more possibilities. The selectors are a core part of Jquery's strength. As soon as your project requires a bit more complexity in selector needs, that's when Jquery steps up and helps out. That's what I've found anyway.