Drupal is a steep learning curve, but its certainly worthwhile. I have read the user manual which helped alot and had to persist through alot of documentation.
Joomla is easier to pick up and get working, Drupal requires you read instructions. Its also more difficult to understand how to theme but having themed wordpress / joomla before Drupal wasn't that much of a big step.
Having said that, Drupal is far less fixed in structure and much more adaptable to a wide range of applications. This is the exact same reason why its hard to learn, because it assumes nothing and needs you to tell it what to do.
I hope that helps. If you are looking for a powerful robust CMS and want to run more than 1 website Drupal is great.
If you need a simple website Joomla is probably the way to go.