Hi, difficult one..I.S.E is less involved in marketing equipment and is a bit tougher without a doubt They both come from the same cradle, Achim was the first GUE tech Instructor in Europe, I think it is a bit personal, what do you need and what do you want to lean? GUE has got some great instructors, especially the old-school experienced guys (I wouldn't mind doing a JJ class with JJ;-)) I will be honest, I am also GUE certified but I never felt connected due to the equipment thing, all these people involved trying to make some cash and wanting to be important...Northern europe is nightmare..I am free spirit, with a huge passion for diving..the rest..naaahhh.nm
ISE is a bit tougher and more open minded probably...
Nevertheless, great agency with some awesome divers !