I would have to say that cPanel is my favorite, it is easy to use, maintain, backup, and there are a very large amount of options. Some hosts even make it look nice with their own logos and such, not to mention WHM is very easy to use, and popular too! There are others like H-sphere and then there are also the custom host ones, like site 5, godaddy, and hostway have their control panel. I say that cPanel is one of the most powerful, makes the user feel free, not controled, and like they have someone of their own considering the fact that the host might have the same control panel, just not with so many options.
cPanel is my favourite mainly because it has more features, more user friendly and many clients are used to and prefer the cPanel interface. Also it comes with an addon fantastico which allows you to quickly install a variety of open source scripts.
cpanel has been an eye opener for me for time reasons but i am losing a lot of programming skills getting used to it as a crutch. The fantastico addon is great, as long as you can keep up with the open source support.
Personally, I like the interface and automation of H-Sphere (pSoft) myself. I think its much easier to navigate, and does not require as much "clicking" as cPanel and WHM to get to where/what you want to do.
Were going to see cPanel is going to be the dominant control panel. It's been in the business for years. Customers love the easy, straight forward (for the most part) interface. Hosts love them too, it's very easy to navigate in, it's not slow, or muggy, and again, it's the most known. Change isn't always necessarily bad, but most people don't like it.
cPanel does not have more features for the end user... it is definately more feature-rich for the admin though. I prefer DirectAdmin because it just works, and it doesn't use a lot of resources. I have had many clients who were used to cPanel go out of their way to tell me how much they now prefer the DA panel.