Explanation:

 In parliamentary form, the executive is formed from the legislature. For instance, in India, Council of Ministers are selected from members of parliament. But in US which follows presidential system has strict separation of power between executive and legislative and the executive does not require the support from the legislature. Hence, it will be more stable compared to parliamentary form. In parliamentary system, passing the non-confidence motion is enough to overthrow the government. Since the government is formed from the parliament which itself composed of representatives from different regions and communities, Parliamentary system allows better representation in government.