Hi Stam and welcome
I don't believe there is a "rule of thumb" regarding this. As I am not an IP, my comments here only reflect my opinion and should in no way be taken as "so"!!!!!!
With the amount of debt that you have, entering into a DMP will take you years and years to pay and there is no guarantee that your creditors will stop bugging you etc.
In an IVA, all interest charges stop, your creditors won't contact you ie phone calls, letters etc and you will be debt free in 5/6 years depending on what your creditors want.
There are numerous Companies on this site and on the internet whom you could approach and put your case to. If you were to post a bit more information regarding who your creditors were, how much you owe them etc, a qualified professional will be along to give you the best advice. If I could throw my penny in - shop around at least 2 or 3 companies before making your decision. Ask as many questions as you can, even if you feel they are trivial. The more you ask, the better understanding you have about the whole process.
Good luck and let us know how you get on.
Sue
Ho Hum! Think I'll bang my drum!
Read My Blog
http://sadsack.blogs.iva.co.uk/