I would not like to see a fully loaded 773 boarding from Prestwick. Its cramped enough when just one 738 or A320 is boarding!
If I was flying that day, I would be delighted that Emirates went to the effort of flying their aircraft 30 miles north, rather than bussing passengers 30 miles south and considering the weather conditions. All things considered, I'm sure your grievance with Emirates regarding this puts you in the minority rather than the majority.