The Electoral Reform Society (ERS) has produced a very good report on the recent Irish General Election, which was by Single Transferable Vote (STV).
The main argument for proportional representation (PR) is usually so the Parliament or Council represents the voters in proportion to the way they vote and is fair between the parties.
The main counter-argument by supporters of the First Past The Post (FPTP), or Winner Takes All, system is that FPTP provides a link between representatives and voters that most PR systems don’t.
As the ERS report shows, STV in Ireland uniquely provides the best of both – fair representation and a strong link between representatives and voters. It would do the same in the UK and elsewhere. Indeed, STV provides a STRONGER link than FPTP does. This is because, with STV, there are typically five MPs for each constituency, so constituents can choose which to approach with their problems and most voters will have voted for at least one of the constituency’s MPs. No longer would Conservatives in Islington North have only Jeremy Corbyn to approach while Labour supporters in Witney have only David Cameron.
STV has other advantages over all other systems, both proportionate and disproportionate. For example, it reduces party power and increases voter power and choice. It can also provide proportionality on any non-party issues that are important to voters. This might be the balance of male and female MPs or the balance between Eurosceptics and Europhiles.
You can visit http://www.democraticaudit.com/?p=20743 for more on this subject, including the ERS’s report itself.