The only benefits of coilovers over conventional strut/spring kits is the fact that height is adjustable, on some kits the damping is also adjustable and some feature camber adjustment too. This allows you to set up the suspension exactly how you want it whereas a spring/damper kit doesnt always give you what you personally want. Obviously a conventional spring/damper kit will perform exactly the same as a coilover kit if it has the same spring/damping/height/camber values, only benefit of the coilover then would be the size of the springs and therefore the clearance for wider and/or different offset wheels.