My experience with whoiscart would be that you need to be quite good at finding out things yourself, and you must be literate in basic PHP and all
Whoiscart is cheap, powerful, but support documentation is quite hard to find, and it can be quite complicating at times to use it- changing the email templates requires you to feel your way around a few PHP and HTML files.
my vote would be for whmautopilot- things should be great once they launch 3.0 with the helpdesk (they say its going to be like perldesk)