Hi,
The Einstein Campuses can be confusing, but hopefully I can give you some helpful information.
Montefiore is the main teaching hospital of Einstein. It's more prestigious, and the residents rotate at Montefiore, Weiler (attached to the Einstein med school), and 1 month at Jacobi each year. This one is the hardest to get into.
Jacobi is across the street from Einstein med school. It's a city hospital, and is much smaller than Monte. You'll find a lot of FMG's there, and they also have a Shabbas program, which attracts a lot of the orthodox Jewish students looking for a program that accomodates their schedule. It's not as competitive as Montefiore to get into, but the attendings are really excellent, since many of them are older physicians who have been at Einstein for 50+ years. The residents rotate mostly at jacobi, with a couple months at Weiler (they do not rotate at Montefiore).
Beth Israel is the Manhattan satellite of Einstein. From what understand, it's more community based- with less attending teaching, but it's in a fantastic location, so a lot of students choose to go there for residency.
Hope this helps. Feel free to PM with more questions.
Moo35.