The President's informal powers are not written in the Constitution. These powers should be used in unique circumstances. These powers include the ability to enact a legislative agenda, sending troops without an official declaration of war, executive orders, and initiatives regarding foreign policy.
Advantages that can be considered about the use of these powers are that it grants the President to act in more swift ways as a response to urgent matters in comparison to following the regular channel, that would be getting the approval of Congress for various matters. Actions executed with the use of informal powers may also aid emergencies that could not be assessed otherwise, like economic matters or conflicts.
Disadvantages include the loss of legitimacy and credibility of the President if actions are not taken well by the public. This also weakens the overall image of the federal government as it means its bodies cannot take care of matters following their own set of rules.
