I had yellow stuff pads on my previous motor (Skyline R33) and was extremely impressed with the stopping power. They are EBC's highest frictional rating pad, only one draw back was the amount of dust they kicked up onto the alloys. I found myself cleaning the alloys every weekend. But I suppose depends on how much of a clean freak you are.
They seemed to last a reasnoble time, even went with the motor when I sold it.
Don't forget also that changing to a higher fricton pad will mean you are more likely to go through discs quicker, but all depends on what the car is used for and what kind of driver you are etc etc.