If you are an Iowa resident you would be crazy to go to SLU. The Catholic schools are notoriously expensive and the difference in "prestige" between the two is probably in Iowa's favor.
Neither school is going to convey a "wow" factor when you go to residency interviews, they are both solid, midwest medical schools with solid match lists. Not a dig against either institution but a fact of life on the interview trail.
It is unlikely that any difference in ciriculum or "feel" would be worth the cost differential -- once again assuming you are an Iowa resident.