I have flown with both civvy and ex-mil, Brits, French, Americans and S Africans.
Post ab-initio training, I guess that really it comes down to the individual. The ex-mil instructors that I have had have probably pushed me harder to obtain perfection and consequently certainly seem better at explaining difficult difficult to grasp concepts. (I'm primarily talking aerobatics and formation work)
Only once have I had to sit with a youngster who was merely hours building and that experience lasted all of 35mins!
Stik