The Icon will ride better. They use Progressive rate coil springs and shocks valved specifically for the Super Duty to get the best ride possible. Also, the Icon includes the caster cams to correct your caster setting.
Icon Vehicle Dynamics 2005-2008 FSD F350 2.5 inch Leveling System - 2008 F250/F350 SRW 4wd - Truck Toyz Store
Icon Vehicle Dynamics 2005-2008 FSD F250 2.5 inch Leveling System - 2008 F250/F350 SRW 4wd - Truck Toyz Store
For a Spacer setup, I'd recommend the BDS as it includes the caster cams. But I would recommend upgrading to the Bilstein or Icon shocks for a better ride (Click the "Configure" button to upgrade the shocks).
BDS 2 Inch Front Spacer Kit - 2008 Superduty 4wd - 2008 F250/F350 SRW 4wd - Truck Toyz Store
Of course, there is also the Bilstein 2.25" system which also uses progressive rate coils and shocks valved specifically for the SD.
I would recommend adding the rear shocks and the caster cams (you can add both by clicking the Configure button)
Bilstein BTS 2.25 Inch Leveling System - 2005-2008 Superduty 4wd - 2008 F250/F350 SRW 4wd - Truck Toyz Store
With any leveling kit the Icon adjustable trac bar is a nice upgrade to keep the front axle centered under the truck. This can be added to any of the systems via the Configure button.
This is not "necessary" for the install, but definitely recommended.