The Seville Luxury Sedan (SLS), base Deville and DHS all have a softer, more compliant suspension, while the STS (Seville Touring Sedan), Concours and DTS have firmer suspensions. The "sportier" models have constant road sensing suspensions which react to driving and road conditions, BUT a variant of this could be optioned in some base packages. 2002.5 and 2003 STS have the exact same magnetic control suspension as Corvette and Ferrari - and GM uses that on several other upscale models now.
The best way to find out what any particular car has in the way of suspension control and springs is to run the car's serial number (VIN) through the sticky post ^^^ "VIN to RPO converter" This will give you all RPO's (Regular Production Options) built into THAT car. You'll need to learn the various RPO definitions - the only way to do that is through familiarity with RPO lists.