Can you provide evidence of a case where it is not true?
I've worked at a ton of Americas Top Hospitals and have seen physicians side-by-side from different tiers of medical schools.
When I was doing research at in the cancer division at Stanford (arguable one of the top programs), there were a ton of medical schools represented by their physicians. My boss for example,
http://www.lpch.org/findADoctor/search/doc.pl?doc=1947&resultSet=1947, went to the university of Puerto Rico Medical School. She's the current national head of the largest pediatric sarcoma consortium in the US.
The other people in the department went to: PCOM, Stanford, University of Oregon, Albany Medical College etc.
I worked at the Harvard hospitals (Dana-Farber, Brigham, Mass General etc.) and again, physicians from every tier of medical school were present (including FMG). For example, this person:
http://children.photobooks.com/directory/profile.asp?dbase=main&setsize=5&last=perez&pict_id=9904390, who is recognized as one of the top pathologist in the country in diagnosing rare tumors (and is a FMG). I only worked in departments that did academic and clinical research.
The only people that seem to care about tier of school or pre-meds and med students... in the actual hospital setting, no one has time to care where you went to medical school. It's not much of a topic of discussion.
When is the last time you were in a hospital and you heard,"Code Blue, Code Blue... basement by cafeteria... we only want physicians who graduated from Stanford, Harvard and a top tier school responding... if you are a DO or went to a school like that medical school in New Mexico, please do not respond... Code Blue. Thank you." Chances are NEVER.
I should add that neither lifestyle nor compensation is affected by where the physician went to medical school (in response to the OP).