I don't know that much about the two schools--but HC Alum makes a good point about location. Williams is really in the middle of nowhere (beautiful, from all I've heard, but in a tiny town not near any city--it also doesn't have the benefits of, say, Amherst, which is part of the 5 colleges.). From some posts in other threads, the transportation also seems to be a bit of a pain. Haverford has much better access to cities/transportation, etc.--if that's important to you.
Of course, Williams also has some things in terms of setting that Haverford may not. Skiing, for example, and breathtaking natural beauty.
I wouldn't think location is a make-or-break choice, but it's definitely something to keep in mind.
Did you get to visit/spend some time at Williams? I would think that would help your decision, as well.
Good luck deciding!
