Short sale vs the auction
At the auction you are not the seller in any way that helps you. The trustee calls it. Fees are already stacked. If there is surplus, it is not the check people imagine. If there is a deficiency, you may still owe. That is not a clean ending.
A short sale is a purchase from you before that happens. The lender has to approve a short payoff. You convey title. The file can end with a release. That is a clean sale when the lender actually closes it that way.
We are the buyer, not your agent. We do not promise a waiver. We do the purchase. What the auction does to your equity.