Is a cooling system more effective run on just water, or with antifreeze/summer coolant as part of it.

i understand the reasons for adding coolant, and i'm not suggesting we all run our cars on just water, i'm just curious as this had come up as a point of discussion at work.

by adding a 50/50 mix of anti freeze to your coolant water does it increase or decrease the effectiveness of it, ie its thermal disipation attributes

are there chemicals in coolant that increase these properties, or is it purely there to prevent freezing rusting and clogging etc?

discuss