Rigor doesn’t always correlate with admissions difficulty, so its hard to say whether Colby is more challenging. Brown would be a good example of how selectivity and rigor aren’t closely correlated.
What you do know is that one costs half as much. St. Michael’s is certainly a very good school and could actually be a much better experience for your child. There are several similar schools in the Northeast regularly marginalized based on selectivity that turn out very successful professionals, including Fortune 500 CEO’s, Pulitzer Prize winning journalists, doctors, billionaire entrepreneurs and federal judges.
There is a similar school in New Hampshire, St. Anselm, that is known nationally for its unique political science program. St. A’s is also famous for a hard limit on A grades. It doesn’t get the time of day on this forum.
In NY, if you were to say “Manhattan College vs Columbia” most would snicker even laugh out loud. The truth is Manhattan College grads make more money than Columbia grads on average and get jobs much faster.
So, you can’t blow your family up over undergrad school.
We visited St. Mike’s and my son received a really great merit award. It is a great school.