Hi Manuel, 
I certainly prefer appimages over snaps.
The reason for that is that - unlike snaps - appimages can be run in a firejail sandbox.
There´s a dedicated option for that: --appimage .
So appimages can certainly be run in a more trusted way.
E.g.: here´s my command for running cool retro term in a closely restricted environment:
cd /media/rosika/f14a27c2-0b49-4607-94ea-2e56bbf76fe1/DATEN-PARTITION/Dokumente/Ergänzungen_zu_Programmen/zu_cool-retro-term/; and firejail --profile=/etc/firejail/default.profile --appimage --private=(pwd) ./Cool-Retro-Term-1.1.1-x86_64.AppImage; and cd
Cheers from Rosika 