well to be honest i only tried mandrake, redhat and slackware 8.1 and 9.
Mandrake and Redhat hide a lot from you.. they are very user friendly.. too user friendly to understand how linux works.
If you really want to know how linux works you can give slackware a try. I'm using slackware 8.1 because I had too much problems when installing slackware 9. Slackware 8.1 uses the 2.4.18 kernel and slack9 the 2.4.20 kernel.
I didn't have any experience with other distro's, but i heard gentoo is good either. but you need an internet connection to install it.
A lot of people like debian..debian is stable but uses older kernels and are a bit out-dated. So what i'm trying to say is that i suggest you use slackware, if you use slackware you'll have to configure your system by editing the config files.. (or you can use webmin). so you need to learn how linux works to work with it
hope this helped