Use coilovers instead of lowering springs when the vehicle needs controlled ride-height adjustment, matched dampers, corner-weight balancing, or repeatable setup changes for different tires, surfaces, loads, or competition rules. A quality package can coordinate spring rate, usable travel, damping range, mounts, and serviceability rather than changing height alone.
Lowering springs remain sensible for a modest fixed drop when compatible dampers, adequate travel, acceptable alignment, and lower cost matter more than adjustment. Either choice changes suspension position, geometry, bump-stop engagement, headlamp aim, sensor calibration, and tire clearance. Decide from measured travel and use requirements, then align, corner-check, and road-test the finished vehicle.