I'm just not sure why is there a versus between those two though... only thing I would say is that I had library problems with Fedora 20, yum is pretty cool even though I don't agree with the naming convention of their libraries/applications, it provides a great implementation of GNOME 3. Honestly Fedora is really polished.
Debian? I think the desktop experience in Debian is lagging behind a lot. It doesn't compare one bit to Fedora. In terms of libraries/applications I don't really care much. I know my way around Debian and I don't think it'll change really much. There are some policies that are pretty stupid... and I find that Debian needs to adopt some sort of semi-rolling model to include minor bug fixes in applications/libraries, which is something Ubuntu and Fedora does well. Stable is rock solid, there's no doubt about that.
Between RPMFusion and PPAs (I'm using Kubuntu right now, you can also mix PPAs with debian as long as you take precautions). I would say that PPAs just wins and has a wider variety. In terms of stability (less breakage) RPMFusion wins.
As for usage, don't expect anything out of this world. I don't think every user using linux is a programmer or loves to toy with nerdy stuff.
- Casual usage (web browsing, checking emails, etc)
- Programming (IDEs, vim)
- Watching series (smplayer)
- Listening music with mpd
- Playing in emulators (pcsx2, dolphin)
- Chatting in Skype and Steam
- Do college work either in LibreOffice or Office
Pretty casual stuff! I think my days of tweaking configurations and checking the latest stuff are slowly going away.