Oligopoly and Monopolistic Competition are two out of about four types of market structures. The various differences between the two will be understood from their definitions. Oligopoly is a type of market structure being controlled by fewer numbers of businesses or firms that are relatively big. In this type of market structure, the level of competition is not as high as what you find in other types of market structure simply because there are a lot of barriers to be faced if smaller firms decide to come in.
Monopolistic competition, on the other hand, is also a type of market structure that has a lot of smaller firms. In this type of market structure, the level of competition is usually high. An oligopoly market is usually formed in the urban region, while monopolistic competition is usually formed in the rural area where there is an absence of big firms or companies. There is no restriction or barrier for businesses under monopolistic competition, and that's why competition is usually high.