Advantages of Parallel Systems
In terms of disproportionality, Parallel systems usually give results which fall somewhere between pure plurality/majority and pure PR systems. One advantage is that, when there are enough PR seats, small minority parties which have been unsuccessful in the plurality/majority elections can still be rewarded for their votes by winning seats in the proportional allocation. In addition, a Parallel system should, in theory, fragment the party system less than a pure PR electoral system.
Disadvantages of Parallel Systems
As with MMP, it is likely that two classes of representatives will be created. Also, Parallel systems do not guarantee overall proportionality, and some parties may still be shut out of representation despite winning substantial numbers of votes. Parallel systems are also relatively complex and can leave voters confused as to the nature and operation of the electoral system.
