Bigtoe has some great points and, yes, a person can basically be the same $ into a comparable srw truck as a dually. Possibly less for the dually if you include new 19.5s in the equation. All depends. Duallies aren't impervious to needing suspension upgrades depending on the weight and user preferences.
AND some of the statements are true about srw components appearing the same and being of lighter or lesser ratings. AND some aren't. Example, my 2500 has factory 1485 U joints, not 1415s, which are also offered in the same truck.
But like most things in life, everything is a compromise. And while a srw is a compromise when it comes to ultimate load capacity and feel good handling, a dually is a compromise on several other levels.
This just isn't something the self proclaimed weight cops are going to tell you though. Becasue, you know, they're right. End of story....