I've played with Knoppix, Kanotix, and Mepis a lot. Knoppix is tailored as a live CD. I really think that if you want to install to disk then you are better off using Mepis or Kanotix because they are tailored for that. In particular, once you install to disk then you will frequently want to apt-get update etc. Mepis and Kanotix are much more amenable to updating from the Debian repositories and will not break as easily as Knoppix.