Ah right, the main advantage I have here is that the dev server also stays running when I go to another branch (since it's a different VM). So I can work on one thing, share it with the team and in the meantime continue on another branch. They can see the devserver / running code, while I am working on something else.
It's especially useful for things like migrations or dependency management. In one branch I could work on something that has some database migrations, and then I can still switch to other branches without having to roll back the migrations.
I didn't know about git worktrees though! I'm going to read up on this.