I have never been to Michigan, but I spent a year in Atlanta and my ex-gf was a med student at Emory, so I spent a lot of time on their campus and got to see a lot of the school's facilities from its student housing (excellent, btw), libraries (pristine), and teaching hospitals (you can eat off the floors at Crawford Long). Plus Emory has affiliations with Grady which is one of the country's largest urban medical centers, so in addition to the cutting edge medicine at Eggleston and Crawford Long, you also get exposed to a diverse array of urban, inner-city medicine.
Emory's student rec center is pathetic, however, though it makes up for it with the quality of its student housing, which has some of the best apartments I have ever seen at a university--then again, for a private institution with the means at its disposal, I would expect no less.
The one big advantage Emory has is in quality of life. Atlanta is a great city, the weather is much more temperate that in Michigan, and it has a lot more to explore culturally. You will have some downtime in med school, and Atlanta has a great nightlife. Emory has no collegiate atmosphere though, so if you're a mich native or even just a big college sports fan, you're out of luck. Atlanta cant compete with the Big House at Michigan, and big ten basketball.
I cannot comment on the catiness of students at Michigan, but at Emory there is a fair bit of competing going on. Since Emory's incoming class size is relatively small compared to most schools, and most everyone is gunning for derm (Emory perennially a 1 or 2 ranked derm program) or ortho or something else competitive, you will work your a** to impress profs--last year several students with straight As in basic science and only one B in rotations got left off for Junior AOA. You could say that competition is tough at every school, but at Emory it is downright fierce.
A good place to start, however, is with each school's match list from the last five years. Find out what fields you are interested in and how much intangibles such as weather, recreational activities, urban nightlife, et matter. Look at where at schools grads have matched, specifically in disciplines you're considering--if you're interested in something competitive, this becomes more important. Also, where would you want to settle eventually? Then rank each school by your subjective score on each metric.