I truly believe that stereo can make a big difference in large rooms too..As I mentioned earlier a 180 degree audience makes stereo tough..
But there are large venues that stereo definitely works..There are rooms we play..on stage with speakers 20-25 feet apart and a 100 feet deep room..the audience is all in front of us...You will hear the movement of the drums and other instruments as well as stereo effects...It may get reduced but not eliminated...When I have the choice ..it is always stereo..
Also mentioned was the Carnegie hall and orchestras..a natural stereo field..You will hear the different sections...that is stereo..location of different instrument groups with in a stereo field..