While you eventually have to pay for Carbon Copy Cloner (assuming you like it), it offers a few features not in SuperDuper.
It can backup and restore your "Recovery" partition.
You can easily select the files and directory trees you want to include/exclude from the backup.
You can use CCC to just move a directory tree from one place to another.
You can use CCC over the network between 2 Macs.
(I've used this to move things like my iTunes library and ~/Library/Application Support/MobileSync/Backup from an older system to a new Macbook Pro, so I could continue sync'ing my iPod Touch.
There are most likely move features above and beyond SuperDuper, I am just familiar with the above.
NOTE: I ALSO use SuperDuper (at least 8 years now) and think it is an excellent cloning utility. SuperDuper has saved me more than once, and I am happy to recommend it. And for the OP's situation of wanting to backup for an upgrade, the fact that SuperDuper is free for a full disk clone makes it attractive.