In the end, it's horsepower that will dictate how fast you can move your load (productive work). The Ecodiesel is great because it produces quite a bit of horsepower early on in lower RPM operating ranges. However, be aware that it only has 240 horsepower. So it will slow down up those hills as it doesn't have the power rating that your 4.6 probably has (which should be around 290 HP), but it will not be spinning as much as a gasoline motor. The benefit though is that the ecodiesel will not lose much power up the hills as it is force induction.
However, the ecodiesel will return excellent fuel economy if you're into that (and diesel is economical where you live).
F-150 V6ecodiesel