Yes there are real differences between Linux distributions, however I have a profound philisophical difference with you. The problem for me, as someone who essentially learned the Mac OS on the Mac plus) Windows (3.1) and X-Windows simultaneously is this sentence:
"The effort of Linux will become nothing more then a college project and history knowledge."
Linux is where it is, for good and bad, for one reason. Micro$oft. Their efforts to remain the default desktop for EVERYONE while defining WHAT you do on your computer has meant that it's getting harder and harder to do many of the things people started using computers for UNLESS you are a power user. In other words, Linux has spread because it is the OS of last resort for many things. Nicholas Negroponte's pulling back from Sugar on OLPC can hardly be a surprise to those who remembered the speech where he called EVEN the Linux kernel bloated. Of course Windows is worse but Andy Tannenbaum was the first to criticize the Linux kernel's size -- back when it was first written. Linus Torvalds is a pragmatist and it should be understood that from the start the kernel has been a pragmatic compromise.
To me what is REALLY upsetting is the number of artists who complain that they are being forced to work on Vista -- with its large memory footprint restricting file size -- by their employers, or the Londone FTSE running Windows Servers when even Micro$oft outsources to a Linux corporation. People are dumb and the choice of OS is generally not rational. It is especially not rational when you look at Linux, however the distributions which CAN succeed is as much determined by Microsoft's determination that all development take place on THEIR platform.
There will ALWAYS be a need for an OS which is optimized for prototyping, and what is WRONG with that?
To answer your question, though, I'm doing this on a dual boot gentoo and slackware laptop. I originally installed Fedora Core, but the combination of KDE4.x and selinux motivated me to go back to gentoo. Unfortunately gentoo can be tricky (you don't INSTALL the kernel, you recompile it) and my problems eventually made it so unstable I had to reinstall. Around then I was playing with dyne:bolic and digging under the hood where I found installpkg removepkg and the other pkgtools in /sbin and /usr/sbin -- yes, despite its Win-friendliness and so forth dyne:bolic is a SLACKWARE derivative. I couldn't resist. After all, Slackware can be stable and you do install the kernel. I chickened out and used an install disk though. In essence, it gave me a stable platform to work out the tweaks of my gentoo install, however having switched to slackware current I managed to make my install unstable enough so I am now sometimes using gentoo to fix that. On the other hand I have yet to figure out why x-windows takes so long to start on gentoo (though it has improved to five minutes from seven) while on slackware it just starts right up. I don't use a display manager anyhow (I start it in text multiuser mode then type "startx" when I'm ready for the gui). Since I do have debian on my other machine and occasionally still mess with Fedora I can assure you that there CAN be SUBSTANTIAL differences between distros, though others are nothing more than remastered derivatives (dyne:bolic, hikarunix...)
Back thirty years ago the Underground was more "respectable" than it is today. More people knew, for example about the Pacifica Foundation and even supported it. FreeBSD and Linux reflect that part of the subculture. Unfortunately it is no longer as respected and we are forced to have our tools defined for us to some extent. What you regard as the bush leagues I consider ONE OF Linux's most important uses because this is precisely an audience Micro$oft turned its back on when they went to Windoze. The idea of it becoming the predominent operating system is repulsive. Red Flag Linux and these other totalitarian derivatives are very clever but NOT USEFUL. I recently read that Suse actually has more market share in China than Red Flag -- though of course the authorities deny this and the source which I won't name is suspect.
I don't want the "triumph of Linux" in other words. I want Chaos. I want choice. I want freedom for everyone to
exploit disruptive technologies. And no I am not alone.
EDIT: Some hours later I won't take this back. But look in the /usr directories for major distros like Debian Fedora Slackware or Gentoo and BELIEVE ME you will see differences. They won't be apparent and first but they are there.