Why not have both?

I find Intrepid Ibex, Gutsy Gibbon, Feisty Fawn, Hardy Heron, etc. to be quite sortable.

Dude, version name is a great vessel for branding and promotion. Most distros have version names and version numbers, it's not hard to dereference a version name and they serve a purpose.

More brand awareness for open source projects == good.

Historically the name came first. Engineering would start working on a new version, Foo, and later on Marketing would decide it if was going to be 1.3 or 2.0

At least that's how it worked in commercial software. Now the names have taken on a life of their own.