I used a stamp on all my Christmas Cards this year - let me tell you, it was the way to go! In the past I have always hand-written my return address, which takes quite a while when you are doing a whole stack, and they get messier and messier. This year, I just stamped each one - so so easy!! And cute.
So obviously I recommend address stamps, (unless you plan on moving soon, then you won't want to commit to a stamp with your current address). Mine is a self-inking return address stamp in a circle, similar to this one: