I have a white 05 mustang with the black 12' Lemans stripe kit from AmericanMuscle. They look like all the other stripes out there and have lasted 5 years now. You can kinda see the white mustang is the back of my profile picture. I have a Black 09 mustang now and am going to order white stripes from AmericanMuscle again for this car.
The only thing that you might not like about the kit is that they are not pre-cut. You have to cut them yourself which is kind of a hassle for the first timer like me, but its not to bad. Just over lap all panels, let the vinyls dry, and then razer blade the excess off. The AM kit comes with a lot of extra stripe too in-case you make a mistake.
To save yourself some serious time though you may want to consider pre-cut stripes. Other than that, the quality of all vinyl stripes I've seen is about the same.