The major advantage to not reaffirming a mortgage in bankruptcy is that the debt will be discharged to you personally.  In other words, if the bank ever has to retake the property and sell it and they can only sell it for less than you owe them they cannot come after you for a deficiency judgment.  But if you reaffirmed the mortgage and for whatever reason could not keep up the payments on the property, the bank could get a deficiency judgment against you.  This is a major risk to reaffirm and one that I see brings hardly any real fruit to the client.