I'm a fan of QF's Y+ but would probably lean to the *Class for the trip you propose.
Other than the pros/cons mentioned, another factor is the number of flights/day SIN-AUS with QF vs JQ. If the JQ plane has an issue, you may be stuck in SIN for some time (not ideal with small children) whereas you have a better (but not 100%) chance of being rebooked/rerouted to get you home in a reasonable timeframe on QF.
Whilst the seats themselves are not hugely different, you might like to consider the seating layouts depending on whether you plan to buy seats for the children. If I recall correctly, the Y+ is 2/4/2 iirc on the A380 (and 747) whereas *class is 2/3/2 from memory.
Any reason why they would'nt put you onto a QF flight? I'm sure I've read of this happening before at HNL and BKK.
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