RE-11 is a competitor with the AD08, focused on dry grip primarily, with decent wet grip. Ride comfort is sacrificed for handling. Road mileage is sacrificed for durability under more aggressive driving.
The S04 is more like the Michelin PSS: aiming to be a balance between wet and dry, ride and handling. They'll generally have a little better life in normal driving, but are less well suited for track conditions.
So the RE11 is aimed at occasional track/autocross use, or those drivers who put dry grip and steering response above all else.
The S04 is the highest performance category of a pure street tire, striking a balance of all the factors that one encounters in everyday driving.
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