Numbers add urgency to the notification icon. These numbers may modify user behavior and add to stress levels by pushing users to pay constant attention to apps. Numbers act as a reminder of how many tasks need to be done. When doing testing designs with numbered badges, users often comment the need to "clean" badges, to tidy up after themselves. This may hurt their focus on their current workflow or task.
It all depends on your business model and value proposition and how much you want to keep your users engaged to. If you don't want the user to unnecessary hooked up to your app go for
If you want constant user engagement like in productivity apps that require the user to take instant action, numbers may make a lot of sense. Please go for
number 3 is a mix of both that should be your last choice.
Please remember one more thing: users may pick up negative feelings if we keep them hooked to an app with little to no value