IMO, U Chicago has a more impressive campus, larger facilities, and an powerful mystique. The potential downside is its location in Hyde Park on the south side, pretty far from downtown, but were I given a choice between the two based on campus alone, (and I won't be, unfortunately), I'd go with Chicago, probably because I'm a north sider and it would be a nice change. Hyde park is also a unique and cute neighborhood with awesome houses. If I were new to Chicago, though, I'd probably choose Northwestern for its convenient location.
I hope you realize that the law building is nothing like the main campus, and is across the park.
I don't understand how anyone can sensibly say that the Chicago law facilities are more impressive.