Who out there has used the two of these or have at least some experience using these two control panels.

Plesk looks very clean and manageable, but is a bit slow as far as the demo is concerned. I've heard that some have problems with auto responders too.

I haven't heard about Webmin too much, but looks like it's loaded with tons of features. I think it's free too? I know dedicatedhosting.com and skynetweb.com use this.

I don't like to rely on demos since you can't really test every feature. Any suggestions?