MDN seems to indicate that querySelector is the newer preferred method:
under the Active learning: Basic DOM manipulation heading.
the same thing seems to be said on stackoverflow:
the stackoverflow question mentions being less supported by browsers, but the answer is old, if we check caniuse:
we see that the support is now good. So seems querySelector and querySelectorAll are the way to go.
If people still use IE8 or older, they need to re-evaluate their life choices