I believe it's the large one which fits the older controllers. The below item listing has zoomed in photos that show the difference between the connectors. Comparing the Adafruit images to that--combined with the age of the guide post I originally linked to--make me believe it's the large one.

Since the connector already needs to be removed to switch the cable positions (red/black swap), I intend to simply switch the connectors when replacing the battery on my newer controller.

https://www.amazon.com/dp/B017TGV56U?ref_=cm_sw_r_apan_dp_613BTWR6KYJZYQ3V2AXE