They're not all working with the same exact information. For example, you could have more inquiries on Experian and Equifax (I know I do!), and that will drag your score down with those bureaus. You could have something weird reporting on one, but if you've checked them all and nothing is amiss, it could be the inquiries. I have an old student loan reporting on Experian as open, while it's reporting as closed on the other two. I've contacted both Experian and the company, and I've gotten notices from both that they've fixed it, so I'm waiting for the next update to see if they finally did (as I contacted them two months ago). Until then, my Experian score is artificially inflated a little over the others because I have an extra postive account on that file.
