Kansas City, Austin: Now top 2 average bandwidth cities in US
explorer.netindex.com
explorer.netindex.com
This seems to use speedtest.net data. I haven't found any concrete evidence, but you can bet that ISPs are prioritizing the traffic - either directly via QoS or via hosting their own speedtest.net server.
In Australia only a few metro areas are shown. You might see a variance of 10x (slower) in rural areas.