Rock-solid advice.Sounds like the "best" answer is a SRW 3500. That is what I use to pull my 42' fifth wheel, and daily drive. Feels great with the trailer behind it. Over 100,000 miles on it and I couldn't be happier.
I know that wasn't the original question but that is my .02.
I have a SRW CCLB and can't even imagine having a DRW. One can learn to live with the dually in their area (no drive-thrus, ATMs, etc.) or maybe they live in a rural setting, but you have to consider you'll be traveling with your 5er a lot, to a lot of different places. Most tourist spots are simply not made for big trucks. It's one thing to have to park at the back of the lot at Walmart, another when you have to park a few blocks away from your destination at tourist areas - it will get old really quick
DRW would "technically" be more stable, but I tow 40' 5er and have zero stability issues or any other truck capability issues.