In order to attempt to answer a question such as this we must briefly describe the Feudal system then look at the advantages of having feudalism as a system and also the disadvantages and then secondly look at the alternatives if there was no such system in place.
Let us first look at the Feudal system itself. The Feudal system was introduced to England and spread throughout Britain by William the Conqueror after 1066 and the Battle of Hastings. Normandy and indeed most of France already had a form of Feudalism in place and King William required a hierarchical system of security which guaranteed him loyalty, particularly in the form of an army. Feudalism was the key. Essentially this was led by the monarch who sub divided his land downwards to Lords and Barons in return for loyalty, security and wealth. This was then passed by the Lords and Barons down to Knights and onwards down to Serfs, Villeins and Peasants at the bottom of this pyramid. The peasants may be given land for themselves in return for labour, produce, rent etc. The people occupying the various levels of feudal society each had advantages, or rights and privileges, offset by disadvantages, or obligations and duties. Typically, people closer to the top, the more powerful, such as the barons and knights, had on balance more advantages than disadvantages than less powerful people, like peasants and serfs, closer to the bottom of feudal society.
As a system lets look at the advantages of Feudalism. If we start with the monarchy.
Advantages :
1) a safer society, if compared to the late Roman empire and to Barbaric invasions. Feudalism divided people who live for fight from quiet people, not wanting to be involved in wars
2) Wars were more diffused but seldom involving civilians. They were a problem between nobles
3) More social secuirty : you were linked to your land or work, but you were sure to have it. Non can take land from you