The Ambassador's issues stem, I think, from the oddly shaped lot it was built on. For me, this one is the worst on Broadway. It has so many bad seats and the street noise is constant. CHICAGO really is the perfect show for the space because it's a musical (which helps drown out West 49th Street) and that it's staged in such a presentation, out front way that it cuts down on the partial view seats on the extreme sides.
The Marquis is ugly, but the thing about it is that there's not a bad seat in the place. Over the years (the first thing I saw there was THE GOODBYE GIRL and the most recent was TOOTSIE), I've sat all over the theatre and even stood in standing room in the back of the mezzanine. There was a perfect view and perfect sound every time. Generally, if I had to choose between a pretty building with sight and/or sound issues and an ugly building with none, I'm going to choose the ugly building every time.