"You are correct that most TT or bumper pulls can be pulled with a SRW truck because there TW is relatively small.
It's when you get into 5'ers and TC's that the pin weight and payload becomes a bigger factor that can exceed the ability of a SRW truck." I agree with the weight issue as most 5ers weight a lot and also demand more of everything from sometimes 6 tires to much more fuel.
A TT like ours has an exceptional amount of room (especially for two people). There is also a nice feature that I have a top the truck that holds a lot.
We have been doing the for many years and have seen those with 5ers that also hold two motorcycles and a couple canoes and till has the good wife driving a separate car with the dogs. To each their own, have a great time as you only go by once, enjoy the ride.