There are a few
1) many of the top schools tend to have more lax trading schemes. This means that you don't have to put as much time into studying to get that H and can pursue things that interest you (another degree, research, theater, community service, teaching, etc)
2) connections. Lots of competitive fields are very small and a lot of the powerhouses in academics in these fields will be affiliated with these institutions. If you have one of these guys vouching for you during residency apps, it's a lot easier to get into a competitive residency. It also means you don't need AOA to match into ENT, neurosurgery, ortho, derm, urology, etc.
3) inbreeding. In all specialties, a lot of top hospitals (MGH, NYP, JHH, etc) like taking their own med students for residency, or like taking med students from similar institutions (so places like Yale will send a lot of students to Harvard hospitals, etc). This is especially important if you want to be in academics or pursue a top fellowship
4) this is more subjective, but the students at these places are some of the most impressive people I've ever seen in my life and I honestly can't begin to tell you how lucky I am to call them my friends and colleagues
5) research. If you want to get involved in really high powered research, this is the place to do it. These schools also have a lot of funding for research in med school, so it's really really easy to do.
6) case diversity. Even as a first year, I've gotten to see patients who have diseases that have fewer than like 100 reported cases ever. That's pretty cool.
7) maybe this is silly but it's kind of awesome to sit back and think "wow, I go to medical school at X how sweet is that?"