Webmin is free, and have many settings and features, but I haven't use it enough to tell more about it.
It's not a userfriendly control panel like cPanel or Plesk. But for a poweruser it could be a good control panel.
It depends on what your preferences are or what you want to do, if you want more lightweight I would say Kloxo, both are easy to install but Webmin is not really easy to use, so don't recommend this for new users.
Some say Kloxo is secure, but personally I had some bad issues with it, so Webmin wins on this one.
One available choice is to use both, or maybe get rid of them and get another one like DirectAdmin.
I just came across this forum and saw this post and had to open an account to share my experiences of 5 years with webmin/virtualmin!
I was looking for a free but powerful alternative to the paid Cpanel or Plex and found the Virtualmin to be a the solution.
Webmin act as the core and virtualmin is a module for webmin to expand its functionality. There is a paid and free GPL version.
The free GPL offers everything the majority of server owners would need. I think the paid version offers extra technical support, but I never used it.
The software comes with installation script that fully installs LAMP (Apache, Mysql, Php) and many other useful tools.
So the following two line of code would do a lot of setup process and newbies and advanced users both could benefit (it better be a fresh install of the OS for this to work).
After installation you have to log into the CP (using https://YOURSERVERIP:10000 and run a wizard process to finalize the setup, which asks your some basic question to customize the server to your need.
The official support forum is great and I could easily search google for issues or question that I had and came across a forum post (many times on the official forum) as how to do something or fix a problem.
The virtualmin interface IMO is modern and useful, but of-course if you have never used a software at first it will be overwhelming. Maybe try youtube to find some tutorials.
Over the 5 years of using it, I have been noticing good improvement and thing that been added or some specific bugs that I noticed but had been fixed. Thus, this is an active project with support.
Virtualmin/webmin offers creation of account, managing users, setting up database, mail server, customize the server, install scripts. It is actually quite extensive. It does both basic stuff and more advanced modification.
Virtualmin VS Cpanel/Plesk
I think cPanel and Plesk are benefiting from their name recognition and popularity, therefore, if you are offering a service to the end-user you could be at disadvantages by not offering these paid CPs. But if you are like me and running your own servers, I highly recommend saving the licensing fee and at least try this free option.