Let's first get two definitions out of the way:

A Parliamentary System is one where the executive branch - the government - is situated within the legislature (the parliament). These systems typically appoint a Prime Minister or similar role, who forms a government usually comprised of elected members of the parliament. The government is directly accountable to parliament. Some countries with this system can have a President or Monarch in a ceremonial function. Examples include Ireland, UK, Israel, Canada.

A Presidential System is one where the executive branch is led by a head of government that is separate from the legislative branch. The President is elected directly, and is not directly responsible to the legislature. The government is not typically appointed from the elected parliament. Examples include the USA, Brazil, Colombia.

Why do I think a Parliamentary system is better? Several reasons, including but not limited to the following:

1. The link between the legislature and the government means that the mandate to govern is aligned. That is, a government can only be formed with the support of the legislature which means that enacting programs and laws is a more efficient process than a Presidential system where the different branches can be acting against each other.

2. It provides for better representation of the populace in government. Because the government is formed from the parliament the specific individuals who the electorate put into office take responsibility for government ministries.

3. Better oversight of decision making. Because the parliament can bring the government down with a vote, the government is more accountable in a real way to the elected representatives of the people. Even with a minority, opposition parties can exert significant influence over government programs and the parliamentary process, with government reporting into it, provides a public forum for government decisions to be scrutinized.

4. Elections when we need them. The parliamentary system generally allows for a flexible period of government, with a maximum duration but no minimum. This means that where there is a loss of confidence in a government or some kind of scandal, the electorate are often offered the opportunity to change to a new government before the maximum period of time has elapsed. This improves democratic accountability.

Not all parliaments are equal, and I personally favour a Parliamentary system that provides for strong representation for smaller and minority views, like Proportional Representation by Single Transferable Vote. I think this is preferable to the FPTP system in places like the UK.

I live in a Parliamentary democracy and so I'm a little concerned my opinion is biased towards it. I (think I) know a reasonable amount about Presidential systems but I'm interested to see where I may need to alter my perspective.

You can change my view by providing ways in which a Presidential system improves upon a Parliamentary system in quality of decision making, democratic accountability, representation etc.

Responses referring to specific achievements of countries are unlikely to be as compelling.

Thanks!