I have been using VestaCP for the API to the backend and built a custom panel. Doing this I have no costs for anything but the servers. (correction i use the payed SFTP plugin). I love vestacp and it's ability to run on anything with easy modifications, updates, low usage, and amazing full API.
Have you try froxlor?
Froxlor is very light and straight forward.
.. when you run into problems you will not have many helpful users to help you
That is why the customers love froxlor!
I get a really good support via froxlor.org Forum and IRC.
If my clients weren't so used to cpanel, I would use VestaCP for my production clients.
The situation that most Hosts have been caught in. The users just love cPanel and you are compelled to stick in there.
As for the user - cPanel is the best choice, even if it's not in the list :shh:
But regarding it from the server performance side it's better not to use any panels at all. Without them server allows more flexible config and doesn't make your hands tight #IMHO :shy:
But regarding the end user - the best choice is cPanel.