I had earlier posted my comparison between Debian and Slackware (see this article). All I left out in the comparison was covered by another appreciative member of LinuxQuestions.org, imitheos, who wrote this very interesting comparison and filled up most of the gaps left by me. I am much obliged to this member for granting me permission to use his post in my blog. Here are the main points comparing Debian and Slackware. I have reformatted the post for readability, but essentially the material has been pasted verbatim. Again, many thanks!

1) Package Manager
Slackware has pkgtools. They are some shell scripts that untar the .tgz files and also write the contents of the package in /var/log/packages. It doesn't handle dependencies.

Debian has apt-get/dpkg
I have used Slackware, Mandrake, Suse, Redhat, (Free/Net/Open) BSD, AtheOS, DGUX, Solaris, CRUX, YellowDog
It is imo the best package manager that exists in the unix world. Many will say that RPM is good. First RPM doesn't handle dependencies well. For the majority of People who use Redhat/Mandrake/Suse/etc RPM is good
For people like me who mess with the OS to see how it works, i have broke RPM many times and even render my system unusable (glibc )

I have yet to break apt/dpkg. Whatever i do it simply works. Gentoo's Portage/Emerge is also very good and handles dependencies, but apt is 10 laps ahead in F1 terminology.

1 point to Debian

2) RC System
Slackware uses BSD init scripts. That is some scripts in /etc/rc.d
Debian Uses SystemV init scripts. That is the scripts are in /etc/init.d and there are symbolic links of them in /etc/rcX.d for the X runlevel.

SystemV are not difficult and with the rc-update and some RC editors, they are very easy, but I (my opinion) prefer Slackware's

1 point to Slackware (Subjective Point)

3) Completeness
Debian is a complete os (especially good for a desktop system) for example. You install the "elvis,vim" packages in both Slackware,Debian. In Slackware vi symlinks points to elvis and if you want you change it to vim.
Debian has the "alternatives" system.
Thatis /usr/bin/vi -> /etc/alternatives/vi -> /usr/bin/elvis
There is the "update-alternatives" command which changes the symlink to which one you like. Very good solution imo.

Also, the scripts of every program are very complete. For example, sendmail' script (/etc/init.d/sendmail) even checks if i have a dialup connection and when it is up it configures the sendmail.cf with my new dynamic hostname.

1 point to Debian.

4) Dependencies
As i said, Debian honours dependencies while Slackware does not.
This good both good and bad.

The good of dependency checking is that when you check a program in Debian all its dependencies are calculated automatically and installed too. With Slackware you must find what they are and install them (from the website or Readme or ./configure ) The bad thing is that sometimes you get to install some things that are not necessary.
For example, when i tried to install mjpegtools it needed the libdv library which is not absolutely necessary for the program to work and in Slackware i didn't compile it. This is again because Debian wants to be complete so it enables all the dependencies of each program when compiling.

I guess 1 point to Debian for most people (although i prefer to have an option like Slackware gives me)

5) Point of view
Debian is a complete os (have i said it again ? ). It has an awful large amount of packages (15490 according to Debian Website, but more if you count the "unofficial" packages in www.apt-get.org)

Slackware is a minimalistic os with the point of view that i give you a simple os and you install only what you want from there (NetBSD is the same)

1 point to Debian for desktop system.
1 point to Slackware for server system (Also subjective. Some may disagree)

6) Installation Difficulty and Time
Both use simple ncurses interfaces with description and everything so they are very easy to install. (I don't know why many people say they are hard)

Debian Installer is more complete and it has many translations (Although many computer terms are always english it feels good to install in your native language) Debian takes more time to install because of the huge amount of packages you have to choose from (for a custom installation)

7) Packages Update
Debian is updated very frequently (Testing/Unstable).
Slackware was being updated very frequently too,but now due to Pat's health reasons it has fallen behind a little.

Slackware tends to be among the first distros to include something. Debian wants to be stable than to be bleeding edge, so some packages take a little longer to be included. (Also, for a package to be included it must be stable for all architectures is mentioned in the policy i think, so that takes time) for example Debian Sarge uses Xfree86 4.3.0 while Slackware uses Xorg 6.8.2

1 point to Slackware