something better? how so? better at doing what?
the site says installing on your hard disk gives you an equivelent to Debian, which is pretty good.
The 2 you mentioned are penetration testing distros?
I came across this while googling them -
http://iwhax.net/index.php/BackTrack - Back track only in Beta but combines the 2 into a live cd it seems, so you could run it from cd instead of a hard drive install (but since you mentioned knoppix you dont want this?).
It's based on slackware, it would be fairly easy to use a distro with no xserver at < 1 GB but once you start using KDE/Gnome and their installed apps, it gets chunky. 1 Option would be to install something like slackware and starting out with JUST the base install using something like fluxbox as your WM, then add bits until you run out of space. Or try something like Gentoo where you compile it all from the get go i believe (never used myself) and so will only be installing the options/drivers/modules/programs you want.
I realise this isn't a step by step or anything, but gives you a lot of info to look into.
oodluck