OK, so first, your worries. One, MIT students have a higher admit rate into Harvard med than students from other schools - and from what I hear they've got a pretty good medical program

. (Even if this wasn't the case, however, why pick based off your major? As certain as you are about it now, it will probably change.) Two, the material here IS hard, but I don't think MIT would be a functioning school if the material was too hard to grasp. Three, don't worry so much about majors right now - most people change theirs anyway. I came in thinking that I'd do BE and go to med school, and now I'm a ChemE major who wants to PhD in biology. Just do what you love, and the future will take care of itself - don't put specific expectations on yourself.
So, yes, Princeton probably does have better food and dorms. Among my schools I had Notre Dame (YUMMY food and a beautiful campus) as well as WPI (I hear the dorms there are palaces). And I had the choice about money, too - a free ride at the #9 engineering school, or going to the best?
Anyway, the real question is - what do you want out of the next four years of your life? To learn what you need to know - or be pushed to your limits only to realize that you can really accomplish anything? A pretty dorm - or one full of culture and personality? A comfortable money situation? Good food? Traditional college life, as portrayed on TV? An Ivy League diploma? Some of these reasons I find good, others I think are silly - but it's really about what YOU want.
Decide what you want college to be like, then pick the college that best fits that.