Difference between the two:
Icons have a clear powder coated finish to protect the shock body.
Bilstein 5100s are CAD plated.
Icons use a nitro steel shaft which is harder than chrome and lasts longer under salt spray tests.
Bilstein uses chrome.
Both issues important in areas that see road salt in the winters.
But the salt can eat the clear on the Icons as well so I recommend spraying down either shock with wd-40 or something similar to prevent any corrosion in the winter months in areas with road salt.
Valving and ride quality are very similar assuming you'd run the 5100s valved specifically for the Super Duty.
Hope this helps.