It is unclear whether you have other collection accounts, or other negative accounts. If you have either of those, then the increase will not be as much. If these are your only negative accounts, and you get them deleted, then your score will significantly increase.
Your "which is better" question has a lot of factors. If you think you'll be applying for credit in 2009 or 2010, or 2011 before they fall off, then why not go ahead and take care of it now? If you won't be apping for anything until 2012, then your score now doesn't really matter as much as what your score will be in 2012.
I'm an advocate of paying your debts, so my thought is, if you have the money, offer a PFD. I also think that even if they don't take the PFD, you should pay anyway, but there are lots of folks that disagree with me.
