If you have not attempted to remove a large decal from a painted surface, especially after it has sat in the sun for several years, you have missed one of life's little pleasures. The glue sets up into some new and exotic chemical never seen by man, and the plastic turns to junk that won't stay in one piece long enough to pull the decal loose. Color fade depends a lot on color of paint, and quality of paint. All paint fades in the sun. Some colors are notorious. Plus, the gluing agent can leave traces in the paint or can directly attack paint when not clear coated. The better the glue, the harder it is to remove a decal, and some decals can grip paint so well that removing the decal lifts the paint (not to mention that some vehicles these days are not very well painted -- look at some of the GM and Dodge products with chalked and lifted paint after only a few years). A heat gun can help lift decals, but it is almost never pretty.
There are pros and cons to each. My point is only that high quality decals intended to be permanent are not easy to remove and should be considered to be not all that much different from paint in the first place.
