Single point vs Ground plane, in audio OP AMP PCB layouts
There are pros and cons for either. 

A signal full ground plane has the advantage that signal 0V is a high integrity 0V and can be relied upon but, not when there are currents flowing of any significance. Despite a ground plane being very low impedance, volt drops can still occur when significant currents flow. How much volt drop being a problem depends entirely on the smallest signal that you wish to amplify.

A star point system avoids those "significant currents" mentioned in the previous paragraph by making sure that tracks carry signals (0v return tracks) do not share with these significant currents. The down side is that you end up with magnetic loops that can have voltages induced from one another and the "significant current" flowing in a different track can be coupled.