I agree with the above posts (I also shot you an email) but figured I'd throw my $.02 in for anyone else in the same situation.
As noted above, there is not a huge advantage to one over the other. The incoming student stats are almost identical (WUSTL: 166/3.6 medians, UIUC: 166/3.5 medians). Faculty with both are outstanding. Both are expensive though UIUC does have the in-state tuition perk if you can take advantage of it.
WUSTL wins in terms of the law school facilities though Cost of Living in Champaign-Urbana is significantly less than St. Louis.
The biggest difference is probably geographic job placement. UIUC places incredibly well in Chicago BigLaw but I don't see our grads going to NYC/DC in huge numbers (though we do send plenty, just not a lot in comparison to those that stay in Chicago). WUSTL might be better for outside the Midwest.
The rankings are pretty meaningless between the two. WUSTL might have hit #19 as part of a fluke and may return to the top 25/top 30, or it may be there for good. UIUC's stats suggest it should be back in the top-25 but I guess we'll have to wait until April 1 to find out if there are any rankings corrections to be made.
As a 2L at UIUC, I truly love it here. I went to a smaller college for undergrad and have really enjoyed my experience at a Big-10 school. The people, faculty, etc, etc have made this an enjoyable time thus far.
As noted above, it will probably come down to where you feel the most comfortable.