Well, part of the problem is all the linux distro's use essentially the same software,and linux is nothing more than a toolchain combined with a kernel that adheres to unix standards.........ie POSIX compliant.
Now, what happens is many people get it in their heads that its like windows so by changing versions you will avoid problems or get what you want, that isnt the case at all, they all are the same underneath.
The differences:
RPM,portage,pkg,and deb-pkg--------these are different pre-compiled binaries that make it easy to install software, most linux distros use one of the above, these allow you to download ready to go binaries like windows uses for example and install them directly, they are nothing more than software install/uninstall scripts
OR with any linux distro that has a compiler installed(most should,many do) you can always compile from the source and install that way
The rest of the differences is how much software a distro has with it, how stable or how much testing has been done on the software before its release, and what versions they used.
Redhat which is now Fedora for desktops is a cutting edge experiment basically, it doesnt come with all that much, uses the RPM pkg management system
Slackware---one of the oldest and original distro's, comes with almost anything you could want, has the biggest user base, uses pkg tool software management without dependency checking
Debian--another one of the originals, many others are based on Debian, it has a big following as well, but development on it lately has become questionable, it may fork soon, it uses deb pkgs and not sure if it does dependency checking or not
Mandrake----similar to what Redhat started,they just took it further, some of it is now payware, lots and lots of automated configuration GUI's, similar to windows in that respect
Gentoo--basically a semi automated version of linux from scratch,uses the portage system for automated download and compilation of software
the rest are mostly clones or "one-offs"
I always recommend slackware, it just plain works and has the best most comprehensive user base and one guy has been in charge of it since the beginning.