A short sale will be pretty bad for your credit report. It will linger for 7 years. This may ruin your opportunity to buy in the new area. On the other hand you need to run the numbers, the last I looked into this, the bank will look at rent and discount it by 25%. So the shortfall of $800/mo (after adjustment) will reduce your borrowing power if you rent it out. In general this is the idea. You rent for a year, and buy into the new area. If you short sell after this, while your credit is trashed, you still have your new home, and $50K less debt.
(Disclaimer - There are those who question the ethics of this, a willing short sale. I am offering a purely business answer and making no judgment either way. I owed $90K on a condo where others were selling for $20K. I paid until it came up enough that a lump sum got me out upon sale. The bank got its money in full)
An article on the differences between foreclosure and short sale.