When comparing SteamOS vs Slackware, the Slant community recommends Slackware for most people. In the question“What are the best Linux distributions for desktops?” Slackware is ranked 5th while SteamOS is ranked 79th. The most important reason people chose Slackware is:
Uses stable, plain-vanilla packages from upstream.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Native graphics processor support
The OS natively supports Nvidia, Intel, and AMD graphics processors.
Pro Streaming service integration (under development)
Valve is in talks with streaming companies such as Spotify and Netflix to bring their features to SteamOS.
Pro For entertainment, it just works
What media center software do for videos, it does for games (and later videos).

Pro Stable
Uses stable, plain-vanilla packages from upstream.
Pro Strong adherence to UNIX Principals
Pro Ideal to learn more of Linux
Follows the original Linux roots. It still sees Linux as a free clone of UNIX so the distribution tries to be UNIX-like.

Pro Package management
Uses standard tar archives with shell scripting as packages.
Pro One more distro which is init based
Some users don't like to install systemd based distros because they increase booting and processing speed.
Pro Oldest surviving Linux distro
Besides Debian (which was first released in August 1993), it is the oldest still maintained Linux Distribution and was first released in July 1993.
Pro Super fast
Pro No systemd
Cons
Con Hard to install
If you've installed Arch you're probably fine, but for those used to simple installs like (Ubuntu to name just one) you should prepare some patience, determination, and painkillers. Good news is, it's getting better (it's very young).
Con Not built around the desktop experience
SteamOS is, first and foremost, meant to act as a gaming console - it doesn't ship with even some of the most basic applications, such as a file manager or image viewer. As a result, using SteamOS as your primary operating system would require a fair bit of work.
Con Not user-friendly
It is made to be KISS (keep it simple, stupid), so you have to do everything by hand.
Con Large size live ISO
One needs to vain 3GB+ data for downloading one slackware ISO.
Con Narrow repos
Doesn't offer the same amount of options as other distros do.
Con Niche/small community
Slackware is its own niche and has a small community.
Con Very slow release cycle
Hasn't updated in 3+ years.
Con Dependency issues
When it comes to dependencies, Slackware shows more issues than many other distros.
