I took dexedrine (almost the same as adderall) for years off and on. I also took modafinil or adrafinil for years off and on, not at the same time. Quitting modafinil seems an order of magnitude easier than quitting dexedrine. Adderall and dexedrine are also highly abusable by some people. Taking more feels good, so people start craving that feeling. I've known people who use up their whole month's adderall prescription in 3 or 4 days. I haven't heard of anyone abusing modafinil that way. Taking more modafinil just lets you stay up longer. It doesn't get you high.
When I was using stims, I actually preferred adrafinil over modafinil. Adrafinil wears off faster, so it didn't interfere with my sleep as much. I didn't really like armodafinil (Nuvigil), the newer one, since it lasted too long. It made it difficult to get to sleep before midnight even if I took it at 5 am.