There may be the advantage of a quicker close at the closing table; but financing the purchase is only one element of a many element process when purchasing a short sale property.
Cash offers tend to be less complicated, many omit the appraisal contingency - which no buyer should ever do. They also tend to be much faster to close - all good. The "but" is that short sales are complicated on many levels - lots of moving parts and all have to mesh to get to the point where cash becomes an advantage.
The main issue right now - and this seems to be nationwide - are the banks trying to get as high a price as possible; to the point of not approving deals and letting them roll into foreclosure. Once foreclosed, the properties are then sold, often above market to buyer's obsessed with the idea of "getting a deal".
AGBeat went so far as to wonder whether this is an orchestrated plan by FNMA -
Short answer - yes, cash is always considered the best route; just don't expect them to drastically cut price or give you any type of special treatment.