Although RPM and DEB are technically similar (just sort of archive), the real difference is between RPM and Dpkg. Truth is, RPM guys thinks Dpkg is wrong by design, and Dpkg guys thinks the same about RPM. For example RPM forces non-interactive installation. Dpkg installations are interactive with built in configuration. In my opinion configuration process built into the package installation itself is completely foolish. Debian guys like it. How can you bring the best of both tools, when two major parts of users can not find consensus what is "the best" I think, this is exactly the reason why we have multiple package management tools.

Apt question is the same. I can easily proof, that APT is technically the worst dependency solver available. And in addition to that, it has completely chaotic syntax. Why do you think Apt4RPM is abandoned, and no distribution officially use it?