I have taken both exams. My Prince2 unfortunately expired. However post the training course for Prince 2, I only studied for about a couple of weeks and was able to pass the exam with flying colors. the practitioner exam is Open Book and situational.
I had to study after work and weekends for a good 6-7 months before the PMP exam. It is a closed book and situational.
Certainly more effort is required for PMP than Prince2.
However, Relevance is relative. If you work for a company that values Prince2 or has adopted it as a methodology (compared to the PMBOK which is a body of knowledge), then they are likely to value that designation.
Hope this helps!