what are the benefits or drawbacks of requiring the president to notify congress before sending troops into conflict

Presidents can order United States' troops to fight when the country is attacked or the attack appears imminent but chief executives from both major parties, either republican or democrat, often do not agree with congress over their ability to differ from a necessary defenses/attacks. This is why they sometimes take the liberty to send troops abroad without the approval of congress. Technically, this is not illegal.

But Congress exists to regulate and control the functions and decisions of the President to monitor that no excess of power is done during his period in office. This is one of the benefits of having to notify Congress before sending troops into conflict. A simple bad decision made by one angry man could lead a whole country into an unnecessary war, that is why Congress is there to analyze the situation and give a thumbs up before it all happens.

On the other hand, Congress could take its time to make a decision. Burocracy does not understand that sometimes the commander in chief needs to take immediate action to protect the nation. This a clear drawback of the necessity of having to notify congress before sending troops into conflict.