Kind of ridiculous, but yarn's CLI just feels better. It's a bit simpler, `install` doesn't really seem like an "add to package manifest" command word, there's the `global` subcommand for managing global command-line tools vs `-g`/`--global`, and no command aliases, which I like more for some reason. For me it's mostly personal preference; ergonomics would be the key difference for me. Plus, the upcoming stuff mentioned in this issue has got me excited!

Edit: also, in my experience using npm for some little stuff recently, yarn is still faster installing packages.

Edit2: I also like the ability to run scripts/commands from the base level of command, e.g. `yarn start`, `yarn webpack --mode production`, `yarn build:web`