en2r said;
There are a number of reasons why Dublin has a superior longhaul network. Most importantly, Dublin has a much higher population than Edinburgh, it has roughly 3.5 times the population.
According to Wikipedia, the population of Dublin is;
Dublin City: 505,739
Dublin Urban Area: 1,045,769
Dublin Region: 1,186,821
Greater Dublin Area: 1,661,185
[2]
Also, according to Wikipedia, the population of Edinburgh is;
City: 448,624 (2001 census)
Greater Edinburgh area (including parts of Fife and the Scottish Borders: 1,250,000.
In addition, Edinburgh's population is increased by about 100,000 students during University terms and the city is one of Europe's major tourist destinations, attracting around 13 million visitors a year.
If you expand EDI's client base to include other towns and cities within the airport's catchment area, I suspect that it will be similar to, and perhaps higher, than Dublin's. e.g. a substantial portion of greater Glasgow has shorter journey times to EDI than to GLA.
Your other points are well made though.