In his book Democracies, Arend Lijphart explores "the operation of actual democracies that approximate the ideal relatively closely--and that Robert Dahl calls 'polyarchies' in order to distinguish them from ideal democracy". Lijphart argues that there are two diametrically opposite models of democracy: the Westminster (or Majoritarian) model and the Consensus model. The basic differences between the opposed models are presented with additional comparisons made with the US political system.
 
 

U.S.	WESTMINSTER MODEL	CONSENSUS MODEL
West	concentration of executive power: one-party bare-majority cabinets	executive power-sharing:  grand coalitions
Cons	fusion of power and cabinet dominance	separation of powers
Cons	asymmetric bicameralism	balanced bicameralism and minority representation
West	two-party system	multiparty system
West	one-dimensional party system	multidimensional party system
West	plurality system of elections	proportional representation
Cons	unitary and centralized government	federalism and decentralization
Cons	unwritten constitution and parliamentary sovereignty	written constitution and minority veto
Cons/West in some states	exclusively representative democracy	direct democracy devices such as referenda