Similar experience here - I never used an obstetrician/gynaecologist - it's possible to use a birthing centre and only see midwives...
Don't feel 'locked in' to the first person you see - ask around - my first question would not be 'which doctor' but 'which hospital' ? Once you know which hospital, then you will be directed to whatever midwives/doctors work at that hospital/delivery suite/birthing centre.
I guess you also may be limited by your health cover - does your health cover give better rebate for one hospital vs. another, or one model of care vs. another...how much are you prepared to pay for a 'gap'...