02/-3 WRX sedans came with 20mm rear sway bars, the late 03's and 04's got shafterd and only got 17mm in the rear
The rear strut tops and springs are shaped differently on the 04's
The rear sway bar mounts are a bit heavier duty on the 04's
The 02/early 03 sedan suspension would be better, only because of the factory 20mm rear sway bar. Otherwise the damping and spring rates are the same on the WRX's