Have you booked with a midwife yet? She's very likely to go with the 'better' date given your history, I would think. I told mine the same thing - 6 days difference and wanted the later date since I was induced at 42 weeks last time. She agreed that would be sensible.
The midwife down here didn't want me to get in touch until I was 16 weeks. However, there is a chance we *might* be moving back to Queensland in January, so I have also been in contact with my old OB on the Sunny Coast - and she is really supportive, however, don't know how willing she would be to go with my dates - ITMS?