Towing fun or should I say stress free towing mostly has to do with chassis and hitch setup and or having enough chassis for the weight and the right weight distribution.
I don't see where the engine really has that much to do with stress or fun. I guess if you were worried if you were going to make it up a hill then it might get stressful, but I really doubt if there are many situations that there really is a chance of not making it. I have only had one situation where i didn't think I was going to make it up a grade but it had to do with a mechanical problem on the truck not the power the truck would have made healthy. It was when the catalytic converter got plugged up on an old f350 I had. By the time I got home it would barely do 25 mph. After I "repaired" the catalytic converter with a steel rod and put it back on it was good as new.