I built a project to compare yarn and npm. See https://github.com/thomaschaaf/npm-vs-yarn

The different shows how much better npm@5 is :)

It installs two node.js projects (react & ghost) and shows how long it takes to do under multiple scenarios (cold cache, installed and lockfile). It is automatically run each day. It also creates an average if one version is run multiple times.

I never used yarn, but I just did some research about the changes in comparison to yarn. Well, actually they are more similar now, obviously (saving by default for example). In terms of speed, npm has improved as well (https://twitter.com/passcod/status/860437637764571140). Even though npm still seems to be slower than yarn (https://docs.google.com/presentation/d/1re-AGrTOf4zmnXXDMTG1...). At the end, I'd say it's about personal preference, they both get the job done.