Time for a serious response from someone who actually has experience with ADR...
The main reason why I recommend the top law schools over a specialized ADR program is that most ADR work requires substantial prior experience in a related field. ADR is an extremely tough field to break into, so it's extremely rare that people go straight from law school. The majority of ADR professionals are subject-matter experts. That is, their primary selling point is knowledge of the type of dispute (family law, commercial, labor, etc.) or industry that the dispute arises out of.
Because most ADR professionals get into the field because of their success in a *prior* career, you should consider first how your school selection affects your ability to obtain good legal experience and make contacts that will potentially become clients. In general, although it's not a rule by far, legal employers are more concerned with the overall reputation of the law school than with specialized programs. Sure, it might be fun and intellectually interesting to be able to take courses in family collaborative law, environmental DR, or international commercial arbitration, but if you're planning on becoming a labor arbitrator, those classes aren't necessarily going to substantially help your skill set or marketability.
However, from your earlier posts about your career goals, it's really not clear to me that law school is even the best route to take. In most states, for most types of disputes, there is no requirement that the ADR neutral be a lawyer since the whole purpose of ADR is to resolve problems outside of litigation. One of the biggest controversies in the field is that ADR is becoming too legalized. There are some users that refuse to hire ADR professionals that are lawyers because they can't view and solve the dispute outside of the legal context. You might be better off getting an MPP, MPA, or an MS/PhD in ADR, psych, or whatever specific type of field you'd like to deal with.
Have you talked to any professional neutrals or lawyers that act as advocates in the ADR proceedings? That's what I did when I was trying to decide between law schools. I was told quite bluntly by one prominent mediator/lawyer to ignore the USNWR rankings. Some didn't even know about the specialty rankings! Anyway, feel free to PM me if you have questions.