We will start with Unix control panels first and review one of the most popular control panels available today. You guessed it right.

1. Cpanel/WHM:

OS Compatibility: Cpanel is compatible with almost all major Unix distributions. To name a few it is compatible with RHEL, Fedora, CentOS, SuSE, FreeBSD, Debian, Madriva, and Trustix etc. Moreover it supports both x86 as well as x86_64 architectures making it a popular choice in the industry.
Features: I can write another article itself if I were to mention each of the features Cpanel has. I would be mentioning just some major features to avoid this. Some of them are:

• Three Different Reseller Systems
• Server Backup and Restore
• Graceful and Forceful Reboot Support
• Ability to limit users disk space, bandwidth, POP accounts, FTP accounts, shell access, SQL databases, lists and sub-domains
• Account Upgrades/Downgrades
• Ability to rearrange accounts (move access between disks)
• Suspension of Accounts
• Ability to Copy Accounts from other servers, including: cPanel, WebPanel, Plesk, CiHost/Spectro, Ensim, Alabanza
• Ability to Host DNS on a remote machine
• Install an SSL Certificate
• Restart Services

(You can find in detail about them at http://cpanel.net/features-whm.html and http://cpanel.net/features-cpanel.html.)

Ease of Use: You cannot really find any fault when it comes to easy usage in Cpanel. It has a very clean skin enabled interface with every option just where it should be. So for newbie users, it is very easy to operate. It supports various skins making giving users the ability to customize the look they want for Cpanel.

Upgrade Availability: Cpanel upgrades are very easy. You can update or change Cpanel versions just on some clicks from within the GUI. It takes care of all control panel related and system related upgrades.

Customization and Add-ons: Cpanel interface is pretty much customizable and you can skin both WHM and Cpanel. Various add-ons and third party modules like Tomcat, modsecurity, resin etc are also available through it. Add-ons like Fantastico and rvskin are popular with Cpanel.

2. Plesk

OS Compatibility: Plesk is a sturdy control panel from Swsoft. It is currently compatible with RHEL, FreeBSD, SuSE, Fedora, CentOS, Debian, and Ubuntu etc for x86 and supports RHEL, SuSE and Fedora for x86_64 machines. It is also compatible with Windows Servers.

Features: Plesk has almost all general features similar to Cpanel. Plesk has various levels of access from Master level to mail user level which distributes operative permissions. Please also have inbuilt multilanguage support. Some other unique features provided by Plesk are gameserver management, ColdFusion support integration with helpdesks etc. The complete list can be viewed at: http://www.swsoft.com/en/products/plesk8/details/ for Linux and http://www.swsoft.com/en/products/plesk75win/details/  for Windows.

Ease of use: Plesk has a clean user interface. The various access levels make it easy to use. You only see the options you need due to the access levels. Plesk skins are also available. Multiple language support makes it easy for non-English users.

Upgrade Availability: Plesk upgrades are available in patches. The process is not automated but you can apply the patches to perform upgrades.

Customization and Add-ons: Plesk has various add-ons available like ColdFusion support, antivirus support, etc. Plesk is not fully customizable but some modules in Plesk do serve custom purposes like gameservers. Plesk powerpacks are other add-ons available with Plesk now. It has some

3. Ensim:

OS Compatibility: Ensim is another good control panel from ensim.com. It is currently compatible with Fedora and RHEL for Linux and Windows Server 2003 all editions.

Features: Ensim does have all general functions like the others. The only difference is it created a chrooted environment (on Linux), which gives a wider local configuration scope for users. Ensim again has various levels of access. Ensim windows can be integrated with different mail servers like Imail, Smarter mail, Mailenable etc. You can even provide ColdFusion support with Ensim. The list of features can be found at:
http://www.ensim.com/products/pro/linux/details.html  for Linux and for http://www.ensim.com/products/pro/windows/details.html  for windows.

Ease of use: Ensim has robust interface. It does not have too many options to deal with but layout and options are placed nicely. Domain level access has almost all similar options like Cpanel.

Upgrade Availability: Ensim upgrades are not that easy. Although there are utilities to do upgrades can sometimes break the entire setups.

Customization and Add-ons: Ensim has an API now so it is customizable more than ever before. Ensim power tools are available as add-ons for Ensim. They are a set of self-installing scripts just like Fantastico.

4. Helm:

OS Compatibility: Helm is a windows only control panel. It is a product from Webhost Automation. Ltd

Features: Helm has all standard windows domain control features. In addition to that, it has integrated billing on the reseller level too. It has support for almost all major payment gateways. Also it can be integrated with mailservers like Imail, Mailenable etc. The complete list is available at http://webhostautomation.com/webhost-11 

Ease of use: Helm is totally windows based so it uses asp which makes it fast. The interface is clean and user friendly. It is easy to use once you have gone through the user mail.
Upgrade Availability: Helm comes in with an inbuilt update utility. The tool backs up the installation and performs the upgrade seamlessly.

Customization and Add-ons: Helm supports a wide variety of software, which can be listed at http://webhostautomation.com/webhost-287  so it can be fully customized. Add-on modules like DonNetNuke installer etc are also available for helm.