Arch Linux is a rolling-release OS, which means that the user is continuously receiving the latest software updates on a rolling basis. This OS is therefore suitable for those who want the latest and most bleeding-edge software.
Debian GNU/Linux is a rock-solid OS and one of the oldest Linux distros out there. Debian exists in three main branches: Debian Stable, Debian Testing and Debian Unstable (sid). Debian is highly used in server environments (Debian Stable) and is known to be one of the most stable distros. However, that stability comes at a price. Debian has a much slower release cycle than most other distros. This means that the software is old and outdated, so if you are looking for a distro offering the latest bleeding-edge software Debian might not be the right distro for you. However, you can also install Debian Testing or upgrade Debian Stable to Debian Testing or Debian Unstable (sid) instead of to get more up-to-date software and a distro following a semi-rolling or rolling release model instead of the regular model in Debian Stable. It is not possible directly to install Debian Unstable directly as no iso images are available. However, you can install Debian Stable or Debian Testing from iso images and then change the repository to unstable (sid) and upgrade the system to Debian Unstable.
RHEL is a rock-solid OS used mainly in server environments where it is very popular. A 100% free-of-charge server OS based on RHEL is CentOS, which can be used if you don't want to pay for a RHEL software License. Fedora is the upstream testing edition of RHEL suitable for both Workstation/desktop and Server use. It exists in both a Cloud, Desktop/Workstation and Server edition. If you want a more up-to-date server with the latest software versions Fedora Server is the way to go. However, it will not be as stable as RHEL or CentOS, which offers older software versions. Fedora is pretty much up-to-date compared to Debian, however, if you still don't think your software is enogh bleeding-edge then you can upgrade to Fedora Rawhide which follows a rolling-like release model. However, using Rawhide is usually not recommended as it is the development version of Fedora and the foundation of what will become the next Fixed/Regular Fedora release. You can also install the latest Fedora Rawhide branched which is the Alpha or Beta version of the upcoming Fedora version. This is pretty bleeding-edge although not as bleeding-edge edge as Fedora Rawhide itself. Even though the latest stable version of Fedora is pretty bleeding-edge it is not as bleeding edge as Arch Linux unless you upgrade to Rawhide. Since Rawhide is the development version and it is not designed, you should probably use an Arch Linux distro instead.
Gentoo Linux is a rolling-release OS, which means that the user is continuously receiving the latest software updates on a rolling basis. This OS is therefore suitable for those who want the latest and most bleeding-edge software. However, it has a reputation of being one of the toughest distros to install and configure. If you want to try a Gentoo distro, it is recommended to start out with the more user-friendly gentoo-based distros named Sabayon
Mageia is a user-friendly GNU/Linux distro based on the now discontinued system Mandriva and Mandrake. Mageia is an RPM-based distro similar to openSUSE and Fedora. Mageia uses URPMI as package manager for handling updates and installation of RPM software packages. However, Mageia has recently adopted the DNF package manager used by Fedora, so probably DNF will replace URPMI in the near future. For a long time Mageia was in top 5 among the most popular linux distros on Distrowatch.com. In addition to Mageia, we also have other distros based on Mageia/Mandriva, e.g. the russian based ROSA, OpenMandriva Lx and PcLinuxOS.
SLE is a popular GNU/Linux distro used for Server and Workstation use in Enterprises. SLE itself is non-free. However you can use openSUSE for free for both Server and Desktop/Workstation use similar to Fedora versus RHEL. OpenSUSE is the opstream testing version of SLE, so if you want to test the latest software on both server and desktop choose openSUSE instead of SLE. This is similar to Fedora versus RHEL and thus openSUSE is less stable than SLE, which uses older software. openSUSE exists in two editions. A regular release named openSUSE LEAP with older software and openSUSE Tumbleweed which follows a rolling-release model offering the latest and most bleeding-edge software continuously. openSUSE Tumbleweed is a stabilized snapshot of openSUSE Factory which is similar to Fedora Rawhide. However, Fedora does not offer a stabilized snapshot of Rawhide.
Slackware is the oldest GNU/Linux distros, and thus the most UNIX-like Linux distro out there. It does not offer the latest bleeding-edge software. However, it is possible to compile new software on top of that
GNU/Linux & BSD are blazingly fast Operating Systems (OSs) that are light on resources. Get more bang for the buck. Moreover, these systems are rock-solid, stable and reliable Operating Systems (OSs) offering high up-times. Finally, they offer multiple and highly customizable Desktop Environments (DEs) to choose from at login. The most popular DEs are: KDE Plasma, GNOME 3 shell, Cinnamon, MATE, XFCE, LxQt, LXDE, Deepin DE and Budgie. With GNU/Linux and BSD you are in control of your OS and you decide how fast and lightweight you want it to be.
GNU/Linux a& BSD offers supreme and efficient protection against Ransomware e.g. WannaCry and other malware, worms and viruses. These systems are so secure that you don't need to install anti-virus software. Usually a firewall is enabled by default and it is recommended. GNU/Linux and BSD are as secure as it gets. Switch to a GNU/Linux distro today and achieve huge annual savings and stay secure.
Far most GNU/Linux & BSD distros are 100 % to download, install and use. You never have to pay for software licenses anymore. These systems are highly customizable and offer multiple Desktop Environments (DEs) to choose from at login. The most popular DEs are KDE Plasma, GNOME 3 shell, Cinnamon, MATE, XFCE, LxQt, LXDE, Deepin DE and Budgie. With GNU/Linux and BSD you are in control of your OS and have the choice at login to determine how fast and lightweight you want to, depending on the DEs installed on your system.