It has probably been 20 years since I did anything with deb and rpm, but I think this still holds true:
The deb and rpm formats had a very different philosophy to handling dependencies: the deb format relies completely on package names, while the rpm format also allows you depend on the existing of files (or other things?). That implies that the doing/deb ecosystem only works if you manage the entire OS, while rpm (at least theoretically) allows you to use rpms in a system managed in some other way. Of course that capability in the package format itself did not mean people used that.
The file formats are also slightly different: dpkg/deb is completely build using tar and ar, while rpm is a custom binary based on cpio. That also made the deb format flexible enough to not have needed any changes in 30 years, which is pretty amazing.
The source formats have a lot more differences, but I don’t know enough about those. From what I remember srpm used to be more powerful, but Debian’s source format has caught up by now.
A nice side effect of only Debian using dpkg/deb, at least historically, was that when you got a deb file it was guaranteed to work on your Debian system, but for an rpm you could never predict if it would work on your RedHat/SuSe/Mandriva/TurboLinux/etc. system.
The deb and rpm formats had a very different philosophy to handling dependencies: the deb format relies completely on package names, while the rpm format also allows you depend on the existing of files (or other things?). That implies that the doing/deb ecosystem only works if you manage the entire OS, while rpm (at least theoretically) allows you to use rpms in a system managed in some other way. Of course that capability in the package format itself did not mean people used that.
The file formats are also slightly different: dpkg/deb is completely build using tar and ar, while rpm is a custom binary based on cpio. That also made the deb format flexible enough to not have needed any changes in 30 years, which is pretty amazing.
The source formats have a lot more differences, but I don’t know enough about those. From what I remember srpm used to be more powerful, but Debian’s source format has caught up by now.
A nice side effect of only Debian using dpkg/deb, at least historically, was that when you got a deb file it was guaranteed to work on your Debian system, but for an rpm you could never predict if it would work on your RedHat/SuSe/Mandriva/TurboLinux/etc. system.