This is an interesting topic, inasmuch as if one asks a question, the reply seems to be "What sort of answer was sir requiring?"
I came away from the Instructor Seminar I attended, last spring, with the understanding that one should hang on to the CAA licence unless there's a valid need to change - ie needing to exercise privileges on other JAA state's aircraft. My colleague, who has just completed his instructor course came away with a strong recommendation from his FIC Instructor that he should get the JAR licence straightaway. He's an ancient aviator like me, so unlikely to be leaping into foreign aeroplanes, so I'm a bit confused. I still feel comfortable with hanging on to my UK licence (ATPL)until the Europeans compel a change but can anyone give me a good reason to do otherwise?