I am casually truck shopping (waiting for 2014 models) and trying to fit a tow vehicle to a future 5th wheel. Most of the 5er models we like are in the 9000lb-11000lb dry weight and 12000lb-14000lb G...
SRW has a lighter curb weight which makes up for some of the lost payload capacity in the area of GCWR due to the DRW's heavier curb weight. Add that to fewer tires to maintain, better fuel economy and and better winter traction I went with SRW a few years ago. Go with a dualie if you are going to tow a gooseneck or 5th wheel every day of the week.