The pro is that it is $27 cheaper
The fare rules may be different - so penalties for chamges or cancellations may be different - check to see what the differences are and that may be a pro or a con or neutral
If there is a disruption to the service, then having to deal with AA in regards to a QF issue is likely to be more hassle than dealing directly with QF - but conversely if there is an issue, it may be able to just rebook onto an AA flight - likely benefit to booking on Qantas directly
FF earnings may vary - depending on what scheme you wish to credit to, check the earnings on the 2 options and see which is better
If all else is equal, I would not book on a codeshare since typically it is easier to deal with problems when you can deal directly with the affected carrier