The comparison is not extremely scientific. I picked (pretty much randomly) 16 apps which are in all three sources, looked up the available version and when it was updated. This subset is not very large. Flathub tends to have popular open source applications well known from Linux distributions. Snap lacks many of these, but has quite a few apps outside the traditional Linux desktop world. And at last Fedora doesn’t have many multimedia apps which include patent-protected codecs (VLC, Kdenlive, MPV,…).
Looking at the table, you can see that the differences are not big. Flathub generally offers the most up-to-date apps having the latest versions of apps in the list except for missing one minor update for Eye of GNOME, it was also usually the first one to offer it.
The results of Fedora are pretty surprising to me. One of the biggest advantages of Flatpak and Snap they claim they have over traditional Linux distributions is that they ship the latest and greatest, but apparently at least in desktop apps Fedora is not behind and offers the latest versions as well (with two exceptions in this list) and often very close behind or sometimes even before the two competitors.
Of course a distribution model like Flatpak still keeps other advantages (and also disadvantages): sandboxing, you can run it on older distributions (e.g. RHEL 7) etc., but if you’re only after the latest versions Flathub and Snap don’t give you a big advantage over Fedora repositories. And if the Fedora Project offers a Flatpak repository built from Fedora packages as we plan, it can actually be a hit because it will be able to offer up-to-date applications and in a much larger number than current Flathub or Snap Store.
|Darktable||2.4.0, Dec 24||2.2.5, Oct 25||2.4.0, Jan 1|
|Blender||2.79, Sept 26||2.79, Sept 11||2.79, Sept 30|
|Corebird||1.7.3, Nov 19||1.7.3, Nov 20||1.7.3, Nov 28|
|GnuCach||2.6.19, Jan 5||2.6.19, Dec 18||2.6.18, Oct 30|
|Inkscape||0.92.2, Aug 9||0.92.2, Aug 19||0.92.2, Oct 1|
|LibreOffice||5.4.4, Dec 20||126.96.36.199, Dec 1||188.8.131.52, Dec 19|
|Nextcloud client||2.3.3, Nov 24||2.3.3, Dec 11||2.3.3, Oct 5|
|Picard||1.4.2, Sept 27||1.4.2, Oct 7||1.3.2, Jul 14|
|GNOME Calendar||3.26.2, Oct 5||3.26.0, Sept 22||3.26.2, Oct 11|
|Evince||3.26.0, Nov 9||3.26.0, Nov 29||3.26.0, Sept 18|
|Eye of GNOME||3.26.1, Nov 7||3.26.2, Nov 29||3.26.2, Nov 15|
|gedit||3.22.1, Jul 31||3.22.1, Nov 29||3.22.1, Aug 3|
|Glade||3.20.2, Dec 15||3.20.0, Nov 29||3.20.2, Dec 10|
|GNOME Characters||3.26.2, Nov 7||3.26.2, Nov 29||3.26.2, Nov 11|
|GIMP||2.8.22, Oct 17||2.8.22, Dec 11||2.8.22, Nov 11|
|HexChat||2.2.14, Apr 12||2.2.14, Feb 5||2.2.14, Dec 12 2016|