Well.. IMHO; but it's probably not what your after; when comparing window managers it really comes down to preference..

The Maemo KDE from penguinbait probably is a bit "easier" for the not-very-geeky user.. as it comes in a easy to install deb and launches within maemo... access to the same software as the main tablet. Qole has the Easy Debian deb's .. but then; while seemless to the user; you are running two X servers side by side.. and for the most part it's not noticeable; but there is a slight performance hit - especially when using it via the img files... and the Debian won't run the Maemo apps straight up..

I think as far as onscreen keyboard both are the same.. matchbox-keyboard or the other one whose name I can't place at the moment... neither are quite as nice as the maemo's built-in OSK; nor do they seemlessly fit around the apps like in the maemo side..

If all you are after is PIM.. and KDE's PIM software works for you.. then great; that should work fine. If you want a full laptop-like system in your pocket.. then try either the Easy Debian; or the Bootable Debian.. but atm the bootable debian isn't quite ready as far as Sound and Video goes..

I really think it comes down to: Debian gives you more software... KDE gives you a (IMHO) slightly better interface; and PIM software - than the maemo default stuff.