There's also an (now a bit outdated) talk compared EasyBuild with Spack and other alternatives like Nix/Guix which I gave a FOSDEM'18: https://archive.fosdem.org/2018/schedule/event/installing_so...
The EasyBuild User Meetings have always been very open to having talks on "competing" tools. Todd (or someone else) giving an update on recent developments in Spack is becoming a tradition (see also https://easybuild.io/eum21/#spack, https://github.com/easybuilders/easybuild/wiki/5th-EasyBuild..., etc.)