It is impossible to say without looking at your full circumstances -- a chat with a few providers will give you a better idea. A lot depends on the amount you owe and the amount you can afford to pay. In an IVA you are time limited, interest is frozen and anything unpaid at the end is written off -- they typically last 5 or 6 years. In a DMP you might still pay interest and you pay until the debt is settled in full --- which can take a lot longer than 6 years.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014 http://foggy.blogs.iva.co.uk