Never deal with Banks without a lawyer. They are bottom feeders.
My clients have all said that their scores dropped 200 to 300 points regardless of if they did a Shortsale or Foreclosure.
Shortsale proposals can be a trap
Banks want every piece of your financial information and your life. They can use this information against you and are likely to, if your information does not match what you had on your loan application. Keep in mind... you have no idea what some brokers put in the application you signed after you signed it.
You can be sued by the bank for fraud and the Shortsale denied.