Here are some rankings by Brian Leiter that are of relevance to those planning a career in academia. Michigan appears a clear winner on these rankings.

Placement in Law Teaching
http://www.leiterrankings.com/jobs/2006job_teaching.shtml

Where Current Law Faculty Went to Law School http://www.leiterrankings.com/jobs/2009job_teaching.shtml

Top Ten Law Faculties in Scholarly Impact,
http://www.leiterrankings.com/faculty/2008faculty_impact.shtml

Most Cited Law Professors by Specialty
http://www.leiterrankings.com/faculty/2007faculty_impact_areas.shtml

In addition, you might want to email some Human Rights Law academics and ask them for advice. Jim Cavallaro (HRP at HLS ) would be a good person to contact for advice.

For SJD, go to Michigan

It's a good question, but I would still go to Upenn. Upenn is a world reknown university with a better reputation and an older tradition. It is an Ivy League institution, which still carries weight in the U.S. Also, according to U.S. News, Upenn ranks better.

Upenn is well known for its inter-disciplinary approach. As an SJD student, it would be very valuable to use this interdisciplinary knowledge and tools in order to produce a better thesis.

I'm not sure what kind of HR scholar you're interested in, but Upenn has world reknown experts on human rights.

Upenn is also located in a more cosmopolitan city. Ann Arbor is just a college town. You will not be able to experience all that the U.S. has to offer.