Well my experience says stay with Mandrake 10.1. It is easy to install has all the features and it is rock solid. The only thing is if you have to compile programs to run on Mandrake it can be a problem. But it will be a problem for any noob.
I do think your biggest consideration should be what graphics card you have, if you have an ATI or NVidia 3D card you need special drivers for 3D support. Mandrake and SuSi will supply them but you pay for the installer. With Fedora you will have to compile it (actually a lot of the dist you just dl the driver from NVidia or ATI and compile it). Knopix does come with the actual driver that is funtional at install. I like knoppix but it has problems on my system (major problems) so I stick with Mandrake 10.1.
The other things I have had problems with are Internal Modems (even none Winmodems), webcams, scanners and types of printers (Lexmark in particular). There are some older sound cards and some 32 bit recording sound cards that have problems but I find ALSA reacts quickly to new cards and the problems may be solved.
I have also used Dedian, Caldera, Red Hat (enterprise and fedora), SuSi, Morphix and Knoppix on X86. :-D
