Anyone within the industry that knows me, knows that I'm a strong proponent of BackTrack. Some within my shop are quick to point out the virtues of BackBox (http://www.backbox.org/blog/backbox-linux-201-released) or Pentoo, but I find that they all eventually come back to BackTrack. There's always some feature that Pentoo doesn't have, or some tool that BackBox didn't see as important enough to include. Do I get smug when I see the BackTrack detractors grudgingly come back to the home that is BackTrack Linux? Of course!
Why am I in the tank for BackTrack? Well, the primary reason is that I work in an isolated lab without an Internet connection. If any of you have ever tried installing an application on a Linux machine without a connection to the vast array of Linux repositories on the Internet, then you're intimately familiar with many of my past headaches. There's always some .tar or .bz2 or .abc123 file that needs to be downloaded to satisfy yet another dependency.
So, I was quite pleased when BackTrack 3 was released some years ago, and I have been tickled pink with every distribution that has followed. I mean, the Metasploit feature alone makes it all worth while.
In the end, I suppose one's flavor of Linux is a matter of taste, but if you ever find yourself in a lab without a connection to the outside world, you might find an .ISO image of BackTrack 5 to be quite useful.