Carbon Copy Cloner has got more useful features like the possibility of cloning OS X Recovery too. SuperDuper doesn't offer that possibility, and without OS X Recovery, you may have problems after restoring the clone because you won't be able to use Recovery HD (you will have to reinstall OS X in order to get Recovery HD) nor Find my Mac.
SuperDuper is also valid, but if you can choose, go for Carbon Copy Cloner. Both of them make bootable clones, so you will be able to start up your Mac from these backups in case your hard drive crashes
An additional thought :
I want to backup only my documents and Pictuers folders.
I have two options :
1. To connect en external HD to the iMac USB port, and to copy + update manually these folders.
2. To add an HUB to my iMac Ports and an external HD to the HUB as a "permanent " connection + install and use the Carbon Copy Cloner App to automatecly backup these folders.
Option 1 : simple , no need to buy an App , needs to update manually.
Option 2 : bad influence on speed using a HUB ,
More cables and components to add to my iMac.
An addition App maybe compatible problems when updating OS X / App updating problems.
Any opinion will be appriciated.