I think he means if you get foreclosed, the bank has no recourse beyond just taking your house. If you sell your house, then obviously you're responsible for the difference.
Credit and taxes -- a short sale is, though damaging, less so to ones creditworthiness than a foreclosure, further, the entire amount of the unpaid principal (in either the short-sale or the foreclosure/surrender case, but foreclosure sales generally return less than a short sale with positive owner involvement would) is taxable as income.