How is Tufts different from a public research university?

What public research university? UMass and SUNY are quite different from Berkeley and Michigan. You mention a “smaller” state university. Smaller state universities are second tier/directional schools. The caliber of student at such schools is quite different that at Tufts.

Top state schools may have freshman classes in excess of 600 students. There are no such classes at Tufts. A student should also be able to get the courses he needs or wants at Tufts compared to even the top state schools. Many students have reported being unable to graduate on time because they were closed out of required courses at even the best state schools.

LAC’s are mostly located in small college towns where off campus housing may be hard to find. Tufts is essentially an urban school with abundant albeit expensive off campus housing.

And of course a state school is subsidized for in state students by the taxpayer.