Check out https://github.com/cli/cli/blob/trunk/docs/gh-vs-hub.md

FWIW gh is built by some of the same people that built & maintain hub.

I use `hub sync` multiple times per day. Essential tool.

It's the only way to stay sane in a repo with multiple other developers merging PRs. Updates all of your branches in the background to the current remote version.

For the time being, hub still mostly helps with git operations, in fact it can be used as a git wrapper/replacement since it supports all of git’s commands.

gh on the other hand seems to very specifically work on GitHub’s non-git features, like Issues, PRs, repositories.

IME for non-git features hub is very slow iirc it's written in Ruby