As someone who has friends in both programs and has rotated at both programs, there really is no comparison.
WashU is a consensus top 10 program if you're into that kind of thing. SLU hasn't filled in the past 3 years, so there has got to be a reason for that, not just coincidence.
WashU combines worldclass faculty, facilities, resources, and name all without the attitude. The people are as friendly and laid back as they come. And for you private practice-minded people, when you talk to some of the private MDAs in the St. Louis area and mention WashU, their comments revolve around the great training and strong graduates that WashU produces.
SLU combines subpar faculty, facilities, resources, and name all without the attitude. The people here are also friendly and laid back. Their "growing pains" have been going on for over 5 years and will probably take at least another 5.
Both places you will work hard. Not at the same level as NW, Maryland, UF, etc. - but SLU and WashU are definitely not cush programs.