cPanel and Plesk are the two that spring to mind as far as trust is concerned, simply due to the wide customer base and constant development and support.
Each human being have own vision of this and own opinion and the TOP web sites have the same opinion.
Maybe there is some way to rephrase your question?
I think you have your answers on the top 3 They're definitely the most requested by users with cPanel and DirectAdmin taking MOST of our requests - but then that's the niche that we're in too.
WHMCS is certainly the best billing application available as for now. However, if someone wants to check another billing application, I would suggest Modernbill