I keep hearing people saying today's SRWs are light years ahead in capacity... I'm calling your bluff.
Two rear tires are two rear tires, and that's the problem. Stronger frame? Maybe but who was bending their frame before? Do you think the frame is so different that the truck drives differently because of it? Do you think the axles are somehow stronger than they were? Exactly how?
The new ones still have exactly the same parallel-leaf spring suspension they always had.
What's actually that much stronger as of recent years are engines and transmissions and that's why the tow ratings are higher.
Both sides are correct. A SRW will tow that trailer "adequately". A dually will handle it better.
Here's the thing everyone seems to miss:
I have been driving duallies as daily commuters for years. If you're already going to drive an extended cab diesel pickup, whether or not it's got dual rear wheels makes almost no difference. Your mirrors stick out further than the rear wheels do. The reality is you already need the same width to fit anywhere with a SRW.
This myth that a dually is a huge behemoth that doesn't fit anywhere compared to a SRW is purely psychological. Just like the myth that a SRW will handle a really heavy trailer as well as a dually.
Look at the rigs the 'hot shot' truckers use. Similar size and weight to a large 5th wheel RV. You don't see them running SRWs, and they are all about whatever works best for the least cost and most reliability. They don't want rear tire blowouts or handling that adds extra fatigue to their driving.