The difference between them is the >extra tag in the Packages-Desktop file for an iso profile
- https://gitlab.manjaro.org/profiles-and-settings/iso-profiles/-/blob/master/manjaro/kde/Packages-Desktop
- manjaro/gnome/Packages-Desktop · master · Profiles & Settings / iso-profiles · GitLab
- manjaro/xfce/Packages-Desktop · master · Profiles & Settings / iso-profiles · GitLab
The question has been asked and the answer is to look into the iso-profile.
And over the years that content has changed very little - most dominantly is changes due to packages removed from the repo.
I puffed together a script to list the differences