The two big advantages to coil overs are that they weigh less and that they give you the same body roll control of a conventional spring that is twice as stiff. So, if you have coil-overs with 450lb springs, you'll get the same smoothness over rough roads as a conventional spring at 450lbs but you will be getting the same body roll control through the corners as an 800-900lb spring. Also, you can usually adjust the ride height with coilovers.
Coil-overs move the suspension point out towards the wheel from the stock location. This means the spring is much more efficient in helping to control wheel travel and body roll. You can run much higher spring rates and still have pretty good ride quality.
Because of their adjustability, the real advantage of coil-overs is in racing applications. You can change springs and suspension characteristics to match track conditions. You can adjust the corner weighting of the car to help turn in and exiting. You can adjust ride height.
For street use, unless you have money to burn, a good set of springs (lowering and/or stiffer spring rates in the stock location) and struts/shocks will serve you well.
A forum community dedicated to Ford Mustang owners and enthusiasts. Come join the discussion about performance, builds, modifications, reviews, engine swaps, classifieds, troubleshooting, maintenance, and more!