JDF, if towing mpg is THAT important to you, then don't you require the max tow pkg anyway? I'm know your aware the 5.0 and Max tow are not allowed together. (thats a whole diff debate)
I'm kinda glad cause that would be a tough decision. To me the payload #s are just too low to even consider a non-max tow truck. But thats just me.
I'm not sure you'll ever get the answer you've been looking for re towing mpg. Thing is there may not be "a" answer. Perhaps the EB does better with 3,000 lbs, but the 5.0l would do better @ 5,000 lbs on flat terrain? Perahps the EB does better with 10,000 going up the rockies?
SO many variables. And then you compound that with 3.73s vs. 4.10s and on and on....
In any event I suspect the difference will be so small, it wouldn't impact the overall decision. But we all have diff criteria. Fair enough.