That would be of much more value to the country in terms of "most benefit for most people." In the end the only people who would benefit from a bridge from Portpatrick to NI would be residents of Portpatrick who could nip across to do some shopping, indeed it might even be faster for them to access NI hospitals etc. if there was an emergency. But your basic point - there's lots better ways to spend money - is absolutely correct especially as there is a simple and relatively low cost solution to this problem by simply moving the location of the ferry port to Troon, which already has a port that Irish Sea ferries used in the past.