Move: "Perth, Scotland" → "Perth, Perth and Kinross", October 2019: Not moved. (discussion archive)
The current consensus is for the Australian city to be at Perth and the Scottish city to be at Perth, Scotland.
The basic debate has been whether the article on the city in Western Australia should be the primary topic, and if so, that it belongs at Perth.
Those in favor of such a move essentially argue that because of its larger population and modern public familiarity with the city, it is the most likely article a reader is looking for when they search for Perth. Metrics including web usage support that.
Opponents for such a renaming note that under Wikipedia's guidelines, the primary topic is also determined by long-term significance. They argue that neither city is the primary topic and therefore both should have a disambiguator term and Perth should be a disambiguation page.