First off, let me just say that a short sale is a lesser of two evils. It should be considered as the nuclear option and only available to those with legitimate hardship. Now, with that out of the way, let us talk about the truth behind what a short sale does to your credit.
If you are considering a short sale, then most likely you have fallen behind in your mortgage. This delinquent arrearages has already impacted your credit negatively. So that is the first thing you need to start considering. Any further delinquency on your part will continue to negatively impact your credit.
Now, one of the biggest differences between a short sale and foreclosure is how it's reported to the credit bureaus. If you foreclose you get "debt discharged due to foreclosure" stamped on your report. A recent conversation I had with a credit expert at Experion enlightened me to the fact that Bankruptcy is the worse thing anyone can do to his or her credit and the 2nd worse thing is foreclosure. She also explained that with a foreclosure it could take you up to 3 years to get a mortgage and drop you credit score about 200 pts or more, considering the previous damage you did by the mortgage arrearages. Where as with a short sale, this message isn't there. Instead you get a message that reads, "pre-foreclosure in redemption". This can result in about a 100 credit score drop or LESS! Not to mention, once the home is sold, it may appear as "discharged" on your credit. It's also important to know, that with a short sale, you can qualify for a loan in as little as 18-20 months later.
All in all, if you have a true financial hardship and the mortgage debt burden is too much for you to handle, then the short sale may be a viable and less credit damaging alternative to foreclosure or bankruptcy.