There are two guys who have worked at both places, possibly more. One left Dragonair after something like 9 years to come to Emirates. It was mostly an issue with his son's health in the smog of Hong Kong, I believe. He has since moved on from EK after 7+ years. The other left Emirates after about 5-6 years and is now at Dragonair. He has been seen on this board previously so he may come along and answer. To be honest those are the only two guys who would really know what they are talking about when answering your question.
Typhoonpilot