There are a few key differences between triggers and workflow that are important to note. First, triggers run automatically when an event occurs, while workflow is initiated manually by a user. Second, triggers can perform actions on the same object that caused the trigger to fire, while workflow can only perform actions on related objects. Finally, triggers can access data in both the before and after states of an update, while workflow can only access data in the after state.
This means that if you need to perform an action based on something happening in real-time, a trigger is probably your best bet. However, if you need more flexibility around when or how an action is performed, or if you need to act on multiple objects at once, then workflow is probably a better solution.