Need more information about what you are looking for in a college. The schools are very similar overall. Both are LACs with engineering. Lafayette has 42% STEM majors; Bucknell has 35% STEM majors.
Size - Lafayette is about 2400 undergrads (no grads); Bucknell is about 3500 undergrads (150 grads).
Location - Lafayette is in Easton, PA, a small city, which is part of the Lehigh Valley with Bethlehem and Allentown, an area of about 800,000 people, about 1 hour from NYC and Philadelphia; Bucknell is in Lewisburg, PA, a small town in the middle of PA, about 3 hours from NYC and Philadelphia.