Try each college’s net price calculator with the various possible number of students in college in order to see what the likely effect of the number of students in college will be at each college (i.e. so you know what to expect for year 3 at each college).
EFC from FAFSA only directly applies to government aid (Pell grants and government loans). Each college may choose its own calculation for its own aid, so using each college’s net price calculator is important.