I've always used cPanel. I haven't tried any others, but honestly I haven't had the need to. cPanel has been great.

I think that DirectAdmin is nice. It's fast, clean, cheap and very easy to customise.

Another vote for cPanel. It's a mature product which clients feel familiar with and we cannot fault.

Also, being possibly the most popular control panel out there, it makes assisting a migrating client in from another cPanel host a doddle.

Steve