Do you typically choose one over the other?

I'm not them, but for me I would use Docker if I am tearing the stack up more than a dozen times a day, and Vagrant if I am doing it less.

I doubt I use either of them correctly. But I do love the way I use them.

Same. I generally try Docker first. With multi-stage builds, you can reduce container build times by a lot (after your first build), as opposed to reprovisioning an entire vm every time you need to nuke your dev environment and start from a fresh image.