DirectAdmin and cPanel both are control panel solutions for your web hosting administration allows you to manage different options of your hosting account. Both are developed by different companies are in use by many different hosting providers. Though both do the same job (hosting account management) by using GUI, users have their likes and dislikes about them. Here are some of the points you make like or dislike:
1. Both are paid but fees are not same.
2. DirectAdmin is an easy control panel which providers you access to your webmail, admin options, file management, database management and other hosting related functions. You will get every option available on your home screen which makes it really easy to manage your hosting account.
cPanel is best for beginners as well as experienced hosting users because its very easy to navigate different options, unlike DirectAdmin, cPanel splits the features into categories, which makes them easier to find. CPanel also provides more features and plugins than DirectAdmin does.
3. Both DirectAdmin and cPanel are very similar yet they have many differences. Both provide you options for server configuration using a GUI (Graphical User Interface) but i believe its cPanel that provide you more options than DirectAdmin, though both do not cover 100% server management using GUI but its cPanel that provide you more options than DirectAdmin. 2nd one leave you with lots of management to be done by root shell (command line).
4. If you go with DirectAdmin, it is expandable, but the cost of adding additional functionality is very high whereas in cPanel, you can add plugins and modules very easily without much or any added cost. cPanel also allow expert / advance users to do their custom code to manage different things at their own and they may develop their own plugins as well.
Bottom Line: For me cPanel is a better option to go with since its very easy to manage your hosting especially if you are a beginner.
DirectAdmin is expandable, but the cost of adding additional functionality is very high. With cPanel, you can add plugins and modules very easily without much or any added cost. Along with the expandability through modules and plugins, advanced users can custom code options directly into the system.