I tested my two Cruiser joysticks with the two 9-pin connectors earlier this evening on my A1200 and they both work fine when connected to the Joystick port using the black connector.
(They're not very good sticks, though.
)
Can't test the grey connector as I have neither a Sinclair ZX Spectrum +2/3 or Amstrad CPC, but I'm not worried about that now.