I believe the Hemi still has more towing ability but in terms of "max tow" it's probably not much difference. While towing though you may find the ED shifts a little less often as it makes power lower down than the hemi which needs to rev higher to make its peak power. When you go WOT through, the hemi should still feel more powerful. The ED will get slightly better MPG numbers while towing though in percentages, the ED might save you 15 to 20 percent on fuel costs depending on where you live and the cost of gas vs diesel.
The hemi has that lifter tick issue which affects a small amount of engines, the ED has its own problems and the numbers there as far as I can see, is that you have a higher chance of engine failure with the ED especially with 4th gen trucks. 5th gen trucks come with the new ED and the jury is still out, they said they fixed the bearing issues etc and so far so good (it seems).
Some prefer the sounds and power of the Hemi, others prefer the low down torque and fuel savings of the ED.