The issue to keep in mind is that if you don't need to become a resident of a Schengen state, this could be your best choice so as to ensure you can travel to other places with no problems. The dilemma is that if you're from one of those remaining non-Schengen nations and intend to visit any non-Schengen country throughout the course of your trip, you will need to know exactly what you need to perform if the immigration office doesn't think you meet the criteria.