What is the correct way to store a Google Maps DrawingManager circle overlay? Should I just store the center as a POINT and the radius in a separate column or store a polygon using ST_Buffer()?
It kind of depends on you needs and dynamic nature of your points and buffer. If the buffer is dynamic I would store the point and make a view creating the buffer. If the buffer is static, you could store it as a polygon using ST_BUFFER(). Either way you can always extract the other.