I'd definitely go with Qantas if you're concerned about the time you get off.
With MAM (I believe) you get a months paid leave per year, 2 free flights per year and a lot more destinations to fly to.
I also believe that 8-9 rostered days off is the norm for the industry (feel free to correct me, if wrong)
With Jetstar, there are no blocks for employees to take leave in, it's unpaid, no free/discounted flights, you can have a maximum of 3 consecutive days off per month.
In my opinion, MAM is the better company to work for.