How would you characterize the essential differences between the Kowalskis' and the DuBois's worlds in Tennessee Williams' A Streetcar Named Desire?

The sharp contrasts between the Kowalski and DuBois worlds comprise the central conflict in Tennessee Williams' play A Streetcar Named Desire. While Blanche DuBois has cultivated a careful facade of refined sophistication and old-world charm that masks her sordid personal history, Stanley Kowalski lives a grittier, blue-collar existence. Even the difference in their last names sums up the type of world to which each belongs: DuBois connotes the aristocracy whereas Kowalski is a Polish name that, in this context, connotes a working class background.
In her first appearance, Blanche wears "a white suit with a fluffy bodice, necklace and earrings of pearl, white gloves and hat, looking as if she were arriving at a summer tea or cocktail party in the garden district," reflecting her desire to appear of good breeding and wealth. However, Blanche's manicured appearance hides a deep insecurity about her fading beauty and prospects of upward mobility, as well as her past sexual indiscretions and drinking problem; believing marriage to be her best chance at salvation, she has crafted the outward manifestation of an ideal "catch."
In contrast, Stanley is described as "roughly dressed in blue denim work clothes," reflecting his lack of pretension. He easily sees through Blanche's deceptions and fundamentally rejects her insinuations that she is socially and intellectually superior to him because of her aristocratic heritage. However, in spite of his perceptiveness, Stanley is an animalistic, cruel character who beats his wife, ultimately rapes Blanche, and feels entitled to be chauvinistic and domineering; he acts instinctually and without remorse. He thus represents the opposite behavioral extreme to Blanche's surface delicacy and refinement. Their worlds are diametrically opposed and incapable of coexisting, and in the end, Blanche succumbs to Stanley's sadistic orchestration of her downfall.