Intro
When you have eventually decided to install Linux you need to face another clinch. In today's Linux market there is always the question about what distribution to install. A friend from the next company tells you about how good Red Hat is, your kid is talking about Debian and your uncle is a big SuSE fan. Most Linux users like to have so many distributions to choose from but it's yet another difficulty for the beginner. That's why I'll try to give you an objective overview of the major Linux distributions.
If you have worked with other distributions and you can tell me about them, please write me. I'll be happy to include your comments here.
Red Hat
Red Hat is the best known Linux distribution on the market. Red Hat is strongly supported by the commercial software vendors, for example SAP or Allaire (now Marcomedia) products. Those companies only support Red Hat. This doesn't mean that this software only runs on a Red Hat distribution, but support is an important point for corporate users.
Another positive point is that you'll find compiled RPM packages for many applications. This makes it quite easy for the unexperienced user to get along. Additionally Red Hat has invested some time in hardware configuration. It is quite good at finding some more exotic hardware like RAID controllers.
Now to the bad side. New major releases of Red Hat often had a lot of bugs. Additionally, many RPM packages are of low quality. This has two reasons. First, RPM packages are available for many RPM-based distributions such as Red Hat itself, SuSE or Mandrake. So if you get an RPM for an other Red Hat version than yours or even for an other distribution, it won't fit perfectly on your system. Second, I think it's because there is no policy as there is in Debian.
RPM also makes it very hard to upgrade the distribution. Updating the machine to a new release is not very different to installing it from ground, so many people don't upgrade for a long time. But as soon as Red hat stops building updated packages (to fix security bugs) for the older distribution, you must either upgrade or compile the software yourself.
And one additional note about my personal experiences. Red Hat is very slow if not inexistent when it comes to bug reports. I once posted a bug report because a new version of a certain package fixed an important security hole. I only got a reply quite a few weeks after originally reporting it.
SuSE
SuSE Linux is a German Linux distribution. Because of this they invest much in localizing their distribution. the support for the German language and ISDN configuration is among the best of the market. Because of this SuSE is the market leader in the German part of the world.
SuSE was one of the first distributions to hide the Linux concepts from the user as much as possible. Much of the configuration can be done with a GUI interface (YAST2 at the time of writing) to ease the change for Windows users.
The downside is that many functionalities are only available with a GUI. You can't automate a GUI application and installing the X Window System on every server is not recommended, primarily because of security.
SuSE is an RPM-based distribution. This means that the packages are expected in the RPM format by default. That's why it suffers from the same problems as Red Hat when it comes to package handling. But the problems are even worse with SuSE, because a lot of RPM packages expect a Red Hat file system.
Mandrake
Mandrake is a French distribution, well known for its quality. It is often compared to SuSE when it comes to usability and localization. Mandrake goes to great length helping the user. A Windows user feels at home very quickly. Like Red Hat, Mandrake has done a good job when it comes to hardware.
Comparable to SuSE, you can do most jobs with a GUI, but Mandrake makes it easier for the experienced user to use text interfaces if they want.
Mandrake is yet another RPM based distribution with all it's advantages and disadvantages. See the discussion about Red Hat and SuSE for more information.
Debian
Debian is the largest completely free Linux distribution. Like the kernel itself it is developed under the bazaar style. This means that anyone can contribute to the project by becoming a Debian developer.
Debian is recognized for its very good stability and its package system. APT can solve package dependencies automatically, supports installing of security patches with no interaction and makes it very easy to upgrade the whole distribution. Because Debian had a policy from early on, the official (and also most unofficial) packages have a very high quality. Also because of APT you can install a Debian distribution directly from an FTP server. And restoring the software configuration when restoring the system can be done with about five steps. (If you're interested in the exact procedure just mail me.)
One disadvantage has to do with the stability. New stable releases are much rarer than new releases of the commercial distributions. Debian keeps the stable release up to date with security patches, though. Security patches are even backported to keep the changes to the stable distribution as small as possible.
Debian isn't optimized for ease of use, so there is no GUI for most tasks. This renders Debian unusable for most beginners. But there are some command line tools to configure certain aspects of the software. (The update-* commands and dpkg-reconfigure)
Slackware
Slackware is popular because there are a lot of small things which make the distribution very sympathetic. For example after installing the system there is a new mail in elm/pine welcoming you to the system and containing some important URLs, etc. Because there are no complex tools it's very easy to trouble shoot. Scripting knowledge is required for a good system configuration, but the configuration scripts are commented very well.
On the other side it's hard for beginners to set up and maintain because there are even less helper tools than there are on Debian. But there is a good install tool. The advantage of this tool over Debian's dselect is, that there are no complicated package dependency schemes. The install tools provides the possibility to install from a NFS server, which makes it very easy to set up large numbers of computers.
(Slackware information was contributed by Darrell Rene Dupas)