When comparing Linux From Scratch vs Debian Unstable, the Slant community recommends Linux From Scratch for most people. In the question“What are the best rolling release Linux distributions?” Linux From Scratch is ranked 23rd while Debian Unstable is ranked 29th. The most important reason people chose Linux From Scratch is:
It is an opportunity for the learner to learn what's behind every piece of program in the system, because you will install and configure all the packages manually. It is also as an advantage to expand your knowledge by searching the possibilities of crafting your unique flavor, for example your own package manager and update schemes.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Best for learning the components, libraries and configurations of the whole system one-by-one
It is an opportunity for the learner to learn what's behind every piece of program in the system, because you will install and configure all the packages manually. It is also as an advantage to expand your knowledge by searching the possibilities of crafting your unique flavor, for example your own package manager and update schemes.
Pro For those who wonder what it takes to create an actual Linux distribution
It's a very useful learning experience; showing the user what is required and in what order, to obtain a running Linux system - from the inside out.
Pro Great for Desktop use
It is great for your daily desktop Linux due it good balance of stability and recent packages - it is also recomended by the debian project as the distro you should choose for desktop systems.
Pro Up-to-date software
Cons
Con Not recommended for Beginners
By creating a Linux system from scratch you will be managing and compiling all of the systems packages by hand, so advanced Linux knowledge is recommended.
Con Takes a while to create the system. Only for those people who would like to create their very own distribution, or just to understand what makes a Linux system tick.
Linux From Scratch, requires the user to download and compile, all the various required system libraries and programs in a ch-rooted environment. This is usually done from within an existing and already running Linux system. This is not really a con, just a note to the new user.
Con Development version
Debian Unstable is intended as a development release, and as such is much more likely to break.
Con Not for users new to Linux
You need to know how to maintain Debian Unstable or you can easily bork your system. There isn't very much information available on how to maintain Debian Unstable either. I was fortunate enough to be involved in a now defunct Linux distribution where a forum member put together a how-to on how to upgrade Debian Stable to Debian Unstalble, as well as a separate forum where users could post tips or ask questions about Debian Unstable. One source I would recommend is the Siduction forums.