Parliamentary systems are unitary in which in executive and legislation are fused together. Elections are held trough a proportional representation system. PMs are elected through the party so voters are voting via party and the party elects the PM. As for pros it is easier to pass legislation because when you control the legislature with little to no competition you can do anything. It is easier to replace the PM with a vote of no confidence but then parliament will be dissolved. Triggering a new election cycle causing general election. Forming a govt. however a con is that coalitions can fail horribly and are easy to fall apart. Thus govt. itself can fall apart easy also there really is no form of checks and balances. The minority does not really get a say I would say look up backbenches they are in parliament but aren't really respected.