I only know about MIT, so I'll tell you why I think you should come here...
Academics:
It's MIT, 'nuff said. Though I should add that EECS just got restructured this year (our famous 6.001 is gone for example), so it's a bit of a mess right now. They're throwing in more (stupid, depending on your POV) requirements and making it harder for people to step up and take a bunch of grad classes early. However, even though many students view the changes negatively, that doesn't mean it's gotten worse. As for math, well math here kicks ass.
Undergrad research:
MIT has an excellent undergrad research program (UROP). They make it extremely, extremely easy for undergrads to do real research (i.e. not bitchwork, but instead publishing something even as 1st author). Professors are happy to get you involved, so even as a freshman, you're just a few meetings away from finding a project. That kind of experience is invaluable when applying to/getting a head-start on grad school & deciding what you want to do there.
Internships, connections:
MIT hosts several large career fairs that attract all of the top companies from across the nation & some international groups. With the exception of your freshman year (unless you have prior experience, advanced coursework, or are just awesome...), it's pretty easy to find high-paying, interesting summer opportunities. Also, get to know your professors; between their contacts & the career fairs, if you want a job, you'll get something good.
Surrounding area, food:
Boston/Cambridge are also incredible cities; there's lots to do and plenty of awesome food (I love eating). Public transportation is very common, so it's easy to get around to wherever you need to go (within the citiy).
Womens, social life:
There really isn't an absence of attractive women on campus (esp with so many other colleges nearby), but there may be a rather large number of unattractive folk on campus. I'm really serious about the first bullet. Having been to several other campuses, it's not like MIT that much different in terms of its student body. What we do have less of are: overall idiots, idiots studying humanities, etc (not to say that everyone you meet will wow you with their intelligence).
Dorm life:
Additionally, depending on which dorm you live in, there's a great sense of community among the students. People help each other with homework, provide moral support, etc etc. It's a nice environment to come home to everyday. (There are also plenty of Greek options if you're into that.)
Parties, Alcohol, etc:
If you're into partying, drinking, etc, MIT's policies are reasonable. Or rather, the enforcement of said policies is quite lax. And of course if you fvck yourself up, there's always...
Medical:
There's a hospital on campus. Some people love it not, but really they get the job done, and it's very convenient to be able to seek care for whatever, whenever. A lot of the doctors there also work at MGH, so there are also many specialists in addition to a comprehensive mental health group.
I mean honestly, at those 3 schools, the quality of your undergrad education is going to be about equal. You'll have to decide where to go based on extra-curricular factors, e.g. undergraduate research, the weather, the people, the overal campus attitude, etc.
I would STRONGLY encourage you to visit as many campuses (along with their dorms!) as possible to get a feel for what the people are like.
I'm fixing to graduate from MIT (undergrad), and I really could not be happier with my decision to come here. Please come to CPW; it's a great chance to attend some classes, hang out with the students, and see what MIT is like.