you probably could save some money on a dual system the real advantage is in ff road situations where the shocks can be slightly staggered so one shock slows the road and when you are jumpig and hitting heavy dis etc the second shock kicks in and eases your ride.
but i have never run duals on my superduty nor do i use it in a way that would really benefit...though with a softer spring and set up right it could be beneficial for me as i do off road my truck a fair bit.
where it will cost yohu is buying 6 shocks instead of four at every replacement but even that wont really nail you to a wall so it kinda depends on what you use your truck for...

 

IMO the real advantage to a dual is when they are properly valved each shock only has to work to rebound and dampen 1/2 the amount of a single

but since most of us never push a single past it's limits then really they are just eye candy or worse yet valved as a single but running duals will hurt your ride

 

My Bilstein duals are designed to be dual shocks (or so the propaganda tells me)
If i didn't already have a dual shock bracket (Rancho) I wouldn't have gone duals because they're just not needed and buying 6 shocks ARE more expensive
But they do look more impressive

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