Using `alien` to install a rpm-package on Debian, or just install it with `rpm`? Are there any reasons to use `alien` to install an rpm-package on Debian, or could I just as well just install the package with `rpm`?

Quoting `/usr/share/doc/rpm/README.Debian`:

> Please do not use `rpm` directly to install packages. Install the `alien` package and use the `alien` command to convert/install a rpm package using `dpkg`. Use of `rpm` to install packages is verbosely complaining on Debian systems (you can disable these warnings by `--force-debian`).

The reason is that, even using the Debian `rpm` package, `rpm` doesn't know about the packages managed by `dpkg`, so it can't use them to resolve dependencies.