I agree. The GI division at Wash U and Michigan are equally strong, both being among the top in the country. Residents from both programs seem to match similarly well in GI. Here's what I found:
Michigan (33 in 5 years)
University of Michigan 11
University of California San Francisco 2
University of Colorado 1
Columbia University 1
University of Washington 1
University of Virginia 1
University of Pittsburgh 1
University of Pennsylvania 1
Medical College of Wisconsin 1
University of Texas Southwestern 2
University of Southern California 3
Northwestern University 1
Emory University 1
Henry Ford Health System 2
Tufts Medical Center 1
University of California San Diego 1
Scripps Clinic, La Jolla, CA 1
Wash U (20 in 3 years)
Washington University 5
Brigham and Women's Hospital 3
University of Pittsburgh 3
Yale University 2
University of Chicago
Mayo Clinic
University of California San Francisco
University of Pennsylvania
University of Alabama
St. Louis University
University of Kansas
The only problem with comparing this data is that the Michigan list is over 5 years from 2003-2007, and the Wash U list is over 3 years from 2006-2008. The GI match was reinstated in 2006, so more than half of the Michigan data posted was from the pre-match era. Don't know how that would affect the comparison between the two lists. Let's just say that they both do extremely well in placing their residents in GI (both placed ~6.6 residents/year in GI!). Therefore, from a fellowship standpoint, it probably won't make that much of a difference which one you choose. Unless there is a specific GI faculty from either Wash U or Michigan that you want to work with, I would suggest that you rank based on your other other preferences such as location and "gut" feeling.