For me the most important differences between a Debian system and a Fedora system aren't package format (no one cares) or package manager (even though apt is better!) or package related tools. The important differences are the results of policies that are different.
How are network interfaces configured? What about firewalls? Where do defaults get set? What tools control runlevel services? What is the layout of /var/? Where is documentation stored? What can be found in /usr/local/? If you have a bug, what do you do? Everything here is different and has nothing to do with packaging as such. In some cases such decisions can be made by the user by installing a different package from the default, but then which was the default was a distro policy decision.
I'm all for working together on things not related to packaging, but I use Debian because I tend to like the design decisions Debian makes. I don't want to see other distribution's decisions creeping in to mine (and I'm sure this is mutual).