Dave, I have used both SD and CCC. My vote comes down heavily on the side of SD. I have it as a download, but that has never proven to be a problem. I set it up to make scheduled backups, and a couple of years ago, when my iMac G5 was out for repair, I hooked my firewire external to an old G3 iMac I had lying around, booted from the clone, and was up and running in seconds. SD is completely reliable, I have reverse cloned from it and it worked perfectly then as well. In fact, I am delaying installing Leopard on my main iMac till SD is compatible, which the developer promises will be soon. He is very responsive to questions and emails, take a look at his site [shirtpocket.com].
What more can I say? It's a great application and I would never have a computer without it installed.