[Pharo-users] When to use Versionner and when to use Monticello

Great, now that I saw these screencasts of Versionner (which I'm still trying to have a hang on) I would like to ask: When do we use Versionner and when do we use Monticello? Putting it in another way: What tasks are only possible through Monticello? What tasks you should be doing in Versionner?