I have the 2002 and 2003 editions. The only difference between the two that I've noticed is that the 2003 edition has more color images along with BW images that are like those on the exam. The 2003 edition also has more review topics....the mnemonics are pretty much the same for both editions.
I'd just buy the 2003 edition just because it has more review products and more images to look at.