Brown is quite grade-inflated, which is good for pre-meds:
http://www.gradeinflation.com/Brown.html
However, that may be partly due to the open curriculum (for non-engineering majors), where there are no general education requirements that could require students to take courses in subjects that they are weak at. Brown also allows dropping a course until just before the final exam (although medical schools may notice and question why you have a light semester due to such a late drop, unless you started with an overload schedule).
Main drawback of Brown with respect to medical school is that getting to interviews at California medical schools is much more hassle than from UCLA. But lower cost and probably more grade inflation are advantages for Brown.
Both schools have on-line class schedules. UCLA’s shows class sizes (pre-med courses are large, except for some honors versions). Brown’s does not show class sizes, although you can make some guesses by the smaller number of lab sections associated with each lecture.