The main advantage is not the obvious one: work experience. After leaving education for good, you will find that employers value relevant work experience above a qualification. Additionally, going straight into work will get you directly onto the career ladder, opening up opportunities for a promotion sooner than if you were in education. All the while, you are earning a full wage.
The only disadvantage comes further down the road where you will likely face a barrier to promotion due to the lack of specific qualifications. However, at that point, you can do an apprenticeship to access those qualifications and skills without having to leave employment.