The first issue on the Hygen repo is "how does it compare to plop". Since I've used plop in past projects, this is where I ended up.
Hygen is built to support multi-team, multi-package repos. In comparison with plop, it seems scaffolding can be split out into multiple packages, files, etc whereas plop tends to operate out of a single plopfile.js which can be meh to work with. I've often ended up with a plopfile that looks like this, for example.
Hygen will parallelize most of its book-keeping to gain speed, but file operations are serially executed to avoid operations stepping on eachother's toes.