There are some strong reasons why you would want to use a formal
decision making process over the a quick 'gut' decision. You probably
know people who approach decision making without researching the problem
and looking at different approaches to solving it. The decision results
are often not the best.
Formal decision making is the process of defining a problem, finding feasible solutions, choosing the best solution and implementing it.
Here is an example. While driving you might come to a crossroads, you can chose to go straight or to turn left or right. If you are not familiar with the area, you will not know which direction to go. You want to reach a certain location. You begin your decision making by obtaining more information. You study your map. You learn that if you go straight ahead you can get to your destination. However, turning right gets you there as well. It is time to assess which of the two choices is best. The direction to the right is shorter, but the roads are not paved. Going straight lets you drive on paved roads. Since it has just rained, you decide to go straight.
You are probably aware of people around you who make decisions without a logical data based approach. The decisions made are usually bad.
In order to make decisions without a reasoned logical data gathering approach, you need a lot of experience time. That means you have to be trained to react in a definite way in a given situation. Then you must make a lot of mistakes along the way before you become a good quick decision maker. Good examples of this kind of decision maker are military officers. They usually won't have time for researching a problem and evaluating alternatives. He must make a decision quickly or jeopardize his mission. Any viable decision, in a military situation, is better than hoping to find a better decision. But to do so effectively, takes an enormous amount of training and the right to make a few mistakes. This is also true of athletes or anyone that is in a time critical position. Experience is what decisions are based on in these situations. Without that training and experience the best line of attack is a rational proven method of decision making. To get consistent results, you need to avoid quick unreasoned decisions. You need to use a good decision making process.