DocBook and DITA both have their places. They're both excellent for single sourcing. DocBook is better for what I call monolithic single sourcing, while DITA is better suited for discrete single sourcing.
If you follow the latest trends or have been to a conference recently, you may find the idea of choosing an XML schema puzzling. Isn't the question really, 'How should I customize DITA to do what I want'? While there are many good reasons to choose DITA, it's not the only schema in town.
First of all, understand that you don’t have to learn it. Every year more and more toolds come out that help place a layer between you and the native XML. In a few years time you will hardly even realise there is XML underneath.