Most antifreeze contains Ethylene Glycol as the main constituent.
Pure Ethylene Glycol boils at 245 degrees Celsius but most of the stuff you buy is diluted with water, reducing the boiling point to around 153 degrees.
A cooling system with a stronger concentration of antifreeze in it will therefore tend to boil over later/at a higher temperature than a weaker concentration.
Above 150 degrees the antifreeze boiling is the least of your worries. Rubber o-rings will be starting to give up and you'll get a rather fatal pressure drop in the system. A pressurised system pushes the boiling point of any fluid up ( a neat water system will boil at 130 degrees in your 155 - the glycol'd version will hang on to that "beyond 150").
Finally, a system with Glycol (or anything actually) dissolved in it will retain more heat than a system containing pure water. That is it will take more heat energy to raise the temperature of the coolant by the same amount.
Interestingly, F1 teams use a Glycol-secret-ingresient-X based "antifreeze" that has the consistency of cheap hair gel and is boil-resistant to over 200 degrees. Cool! (or not).
Prof. Ralf S.