For clarity’s sake for the OP, 3+2 programs are not MS programs. They are 3 yrs, typically at an LAC, with a transfer for 2 yrs to a university with an engineering program for 2 more yrs. It is a 5 yr path for a BS engineering degree.
My personal perspective is that for strong math/science kids that it is a poor choice. Most students, especially those who know what they want to pursue and have had a rigorous math and science high school education, will be better served enrolling directly in an engineering program and using that 5th yr for co-oping instead. Not to mention that for a student concerned about cost that a 3+ 2 program is automatically a 5th yr of expenses.