When was the last time you used Mercurial? Git being 10 times faster seems dated. Especially if you're using Facebook's fabulous Mercurial extensions, which actually make Mercurial faster than Git.

https://code.facebook.com/posts/218678814984400/scaling-merc...

There are no version numbers in those benchmarks, nor any way to reproduce them. So take them with a few grains of salt.

In particular, how old was the version of git they were testing with? Were they using SSDs?