the stock WRX lateral links and trailing links use a soft rubber bushing in the link/arm ends. most aftermarket links/arms will use either a spherical bearing/pillowball or hardened urethane. this results in more rear end feel, and better control of the rear end alignment under load. most of the aftermarket rear lateral links i.e. JIC, Cusco, Hotchkis (not the STi links though) are adjustable, allowing you to adjust the rear camber and toe settings without using camber bolts. i know for a fact that the Hotchkis rear lateral links allow you to run up to -4.0 rear camber.