There is no "better", it all depends on how much you want to drop the car (1.5 inches) and what type of driving you'll be doing.
If you want a 1.5 inch drop, and its basically a street car, I would go with the Eibach Pro-Kit lowering springs
http://www.stangsuspension.com/store...p?idproduct=82
You will need CC Plates when lowering. Lowering the car adds negative camber (tires leaning inward) which will cause inner tire wear. CC Plates solve that issue. Here is a link
http://www.stangsuspension.com/store...?idproduct=478
If you still have the original shocks and struts in the car, that is another strong suggestion.