Why is flatpak so much bigger than snap (at least for Okular)?

Question

I was looking at the best way of installing Okular in Xfce, avoiding too many dependencies. While apt mentions 100 dependencies in a 19 MB download, taking 101 MB on disk, I have tried flatpak and snap: the first was added to the Software Manager by opening the file org.kde.okular.flatpakref, but I am announced that 798,8 MB will be downloaded in total. 2,7 GB more disk space will be used

Installing as snap (sudo snap install okular) I see a download in terminal no bigger than 1-2 MB. /var/lib/snapd/snaps/okular_73.snap has 21 MB and /snap/bin/okular has 14.5MB. Are there other (bigger) files stored with this snap or not?

Is that flatpak announcement false?

Why the huge difference?

Is the snap Okular incomplete? (By the way, it stopped working.)

Answer 1

Installing the okular snap will also pull in the core snap (which you may already have) and the KDE frameworks snap (which you also may already have) which is why it looks smaller than the flatpak. People who already have many of those flatpaks will likely see the opposite to you.

Take no notice of the file size in /snap/bin by the way. That's not a good measure. But looking at the compressed snap size (along with the core and kde frameworks in /var/lib/snapd/snap) is a good measure.