Phase response is the relationship between the phase of a sinusoidal input and the output signal passing through any device that accepts input and produces an output signal, such as filter.https://en.wikipedia.org/wiki/Phase_response.
For example in this article http://www.ijettcs.org/Volume1Issue3/IJETTCS-2012-10-23-080.pdf.
This figure shows that phase response of GA as it approaches towards the zeros. Hence phase response of GA is much better. Approaches to zeros that meant phase response is better,why?