I have a SRW diesel pulling at my limit and have done great, however, if I had it to do over again, I would get a dually. After towing for a while, I finally figured a dually would let you get safely to the side of the road with less drama than a SRW in the case of a blowout. Unfortunately, I experienced that about 5 weeks ago. I did get to the side of the road safely, but there was more drama than I wanted. Fortunately, I didn't leave any stains in the seat, but there were a few seconds where I had to steer out of a possible jackknife while the trailer was pushing pretty hard.
One thing to consider before getting a dually, check with your insurance company. A friend had a F350 and was able to insure with USAA, but he traded for a F450, and USAA dropped him because now he had a commercial vehicle and USAA would not insure it.