It's trade off, but if you want to go into an applied field like Educational or Clinical Psychology having a placement is incredibly helpful in getting the necessary experience. The biggest hurdle psychology graduates face is getting the first foot in the door and standing out from the crowd of other psychology graduates. A placement not only gives you that experience, but also some contacts in that field.
Some of those avenues are only open to undergraduates on a particular course. For instance, my clinical service only takes undergrads on placement years from our local university, as we have the HR agreement and paperwork in place. In contrast, if grads approach us independently for experience we aren't able to take them on because that stuff isn't covered.
It is less helpful if you have contacts already in that area and can line up a relevant post yourself. For example, if your mum is a headteacher and you are interested in Ed psych, you could probably put something comparable together with those connections. In that case, it may not be worth the extra years fees.