On the other side of the coin, FAA licence holders might be able to convert to JAA licences more easily if the FAA examination process was a bit more rigorous.
A bizjet friend of mine recently did his FAA theory exams - he said he just bought a CD containing all 700 FAA multiple choice questions, it took just four hours to learn off by heart all the answers, then he took the exam, and passed. He said that as far as he was concerned the FAA licence was worthless as it was so easy to pass the exams.
The JAA exams do not allow you to do this - you actually have to study and understand the material, not just blindly learn by heart the answers to the exam questions.