I was accepted to these schools, but received the guarantee transfer option for BU. I need some expertise into the pros and cons of each schools. I am thinking about studying either Aerospace, mechanical, or electrical engineering.
Bottom line cost of each school? Guaranteed Sophomore Transfer is not an acceptance. It is an option to transfer if you meet the stated criteria.
Of these three Universities, only WPI actually has a four year BS accredited program in “Aerospace Engineering.” The only other University in the state with an ABET accredited BS program in Aerospace engineering is MIT. See http://main.abet.org/aps/Accreditedprogramsearch.aspx
For WPI read a recent “pros and cons” posting by parents of current students @ http://talk.qa.collegeconfidential.com/discussion/comment/22181274#Comment_22181274
What are you looking for?
The WPI Plan is not the same program as BU or U Mass with a different name? Find out what it is and does it seem fit you? U Mass and BU may be much more like each other, but are not the same in every respect. By way of example, do you want to be in Boston or Amherst?
What sort of activities do you need to make your day? Can you discover and get involved in those interests at your selected University. When you focus your questions, we can help you find answers, but we cannot form your questions.