For accurate waypoints based on sonar returns for a console unit, you would want the GPS antenna at the transom where the transducer is.
"Pros" using the Minnkota Ultrex would have a heading sensor that talks to the iPilot via Bluetooth. That is a white puck also.
Additionally a GPS antenna with heading sensor is used to stabilize the chart view when at very slow speeds. Point1 is the Lowrance version, and AS GPS HS is the Humminbird version.
Humminbird Helix 12 CHIRP SI, 1198c SI, 1198c SI, ONIX 10 SI NT, Helix 7 CHIRP SI GPS G2, SOLIX 12 SI, 360, RC-1