Academically, both are excellent schools. Both will give you broad clinical experiences especially with Bellevue (NYU) and Jacobi (Einstein).
I graduated from NYU med, however I did spend 1 summer doing research at Albert Einstein during college.
If you are lucky enough to have a choice, congratulations. All the private NYC schools are excellent and I would challenge anyone who tells you that going to one over another will give you an advantage, it really is not true.
However some factors to consider regarding Einstein, the neighborhood, while safe is quiet/boring. The summer I spent there I always tried to flee that part of the bronx. That however may be an advantage for you as it could provide less distractions. The housing situation at Einstein was poor, the residential towers were very cheap but very run down. The AC and elevators broke every week during my summer there! NYU's Rubin dorm is also pretty poor, however after suffering there a year, you could move into nice 3 bedroom apartment in Greenberg across the street (i loved it there). The benefit of living in the bronx though, living off campus is entirely possible due to lower rent.
Also the clinical sites affiliated with Einstein are all over the bronx and some in other borroughs (sp?) My friends complained about the hastle as they had to take car services to get to their hospitals as only Einstein and JAcobi are within walking distance. NYU is great as Tisch, Bellevue, the VA, and HJD are all close.
A major difference between the schools is the academic push of the schools. NYU is a more research driven school where most of the students (85% in my class) participated in research and few went into primary care activities. A large % of students at NYU end up in academics. I dont know if that is a product of the students they take or the curriculum they are exposed to. Einstein is very primary care oriented, they have a family practice rotation (absent at NYU). Looking at the match lists, more Einstein students do primary care specialties. I had a friend who chose Einstein for this reason as she felt she would be better prepared to be a PCP.
Hope this helps