Many people claim that cPanel is a horrible control panel. However, most people who say that massively oversell and blame the server's sluggishness on the control panel. Overall cPanel is not that bad in terms of being a resource hog. If you're going to be running on a low-end VPS then, I would personally suggest DirectAdmin as it will help salvage resources that you'd want to use for your site instead. However, anything w/ 512MB RAM or more should run perfect w/ cPanel unless you heavily oversell your resources (but that's not cPanel's fault now is it?). cPanel has nice add-ons such as RvSkin, cPanelXP, and even Fantastico is a good marketing tool.
H-sphere is also a very nice control panel as it is one of the only that allow you to have single servers to run a single service (e.g. an SQL, DNS, and Mail box). This allows you to easily spread out your resource usage. Also, H-sphere is very scalable along with it's own billing & support ticket system.
There is no best control panel, there is the only the control panel that's best for you. :devil:
Just my 2 cents.
-[Unknown]