<p>I am not quite sure where to start with this question. I do know a few things about both schools as I know several students at BMC and UCSD and have visited BMC 8 times over the last three years and UCSD 3 times over the same time frame. Many years ago I almost took a job at Scripps. I also studied in Philadelphia so I also know a bit about both cities.
I will first discuss the engineering issue. I agree that this should influence your decision to the extent you are committed to engineering. If you want to do engineering I would go to UCSD. Could do BMC/Cal Tech or possibly BMC transfer Swarthmore etc if you later decided on engineering but if engineering is your career choice now I would go to UCSD. Engineering has good career prospects and decent salaries.
If you are mostly undecided you must know that there are major differences between the two schools. Lets start with location. BMC is in a upscale suburb of Philadelphia while UCSD is in a upscale suburb by the ocean in San Diego. Weather in San Diego is almost perfect with mostly sun with moderate temperatures all year except for the marine fog that comes in once in a while and rain in the winter. Philadelphia is temperate in the spring and fall but cold in the winter with snow. Hot and humid in the summer but this is mostly outside the school year.
The living situation is also very different.
One school is large and the other small. Both schools are safe. BMC is a residential school with almost 100% of the students living in dorms. UCSD is not a residential campus with perhaps 30% in dorms with the rest either living in apartments nearby or commuting from home. BMC has nice dorms with mostly singles while the UCSD dorms are generally described as crowded. There are strict residential rules at UCSD. Students seem to like the food at BMC while UCSD food is described as ok. Both campuses not noted for lots to do. BMC heads to Haverford or Swarthmore by campus bus or train to Penn or Philadelphia. Students also sometimes head to New York by bus. UCSD heads to the beach or to San Diego. UCSD also tends to empty on weekends. There are transit services in San Diego but having a car is really helpful with leaving the school. Not as necessary to have a car at BMC. The BMC campus is less than 140 acres so walking everywhere is easy. Even the train station is only a short walk. UCSD has buses or the students use bicycles or walk.
The student body is also very different. Female vs Co-ed is probably the major distinction. BMC is otherwise very diverse with about half of the student body coming from the east coast and the rest from everywhere else. Do not agree with the observation of a lot of left wing hippies at BMC. BMC racial breakdown is something like 15% asian/5% black/<5% Hispanic and American Indian and ~15% international. UCSD is ~40% asian/10% Hispanic and few blacks. UCSD is almost strictly Californian with a majority from Socal. Both schools, especially BMC lean left. UCSD is very science oriented with lots of pre-meds. BMC seems better balanced in this regard. Students at UCSD are very very competitive and work hard. This is probably secondary to the pre-meds. BMC students also work hard but are very collegial due to the traditions of the college and honor code.
The academic style is also quite different. BMC is based on small classes and seminars with lots of writing. UCSD is based on large lectures/TAs and multiple choice exams. Students get a lot of attention from professors and deans at BMC.
UCSD is much more about anonymity unless you seek out the professors or TAs.
It depends on the individual student to decide which system works best for them.
UCSD has many more majors and areas of study available as a large Research University. BMC students have to travel to Haverford (almost next door), Swarthmore or Penn (not that easy) to expand their options.
I should also note that there is currently a major problem with getting the classes that you want at all the UCs. All of my daughters friends have had to go to summer school to get the classes they need to graduate. Several have expressed the opinion that without their AP credits and summer school they would not be able to graduate in four years. This decrease in class availability has also in some cases led to relaxed graduation requirements. This is not a problem at BMC.
The last and perhaps biggest issue is the question of fit. If you have not visited and done a sleepover it may be hard to tell if you will fit into BMC. The honor code and traditions among other things make Bryn Mawr a rather unique institution. Some will love it and some will not. Bryn Mawr is really in many ways a large sorority with a very diverse group of women who are very academically driven. This may or may not be you cup of tea. UCSD may be a safer choice in this regard as I do not think fit is as important in a large rather anonymous institution.</p>