We've done DXB-MEL and MEL-DXB often in J class and a couple of times in F via upgrade with miles. Personal preference having done 777 and A380 is for the 777 - firstly you get a visit to the lounge in KUL or SIN rather than the long haul and secondly a couple of window seats suits us better than the staggered arrangement on the A380 - those seats feel like you are in a sleeping bag as well! There's too many in J on the big plane and gives a feel (personal thing) of cattle class business to me. Bar handy but you can ask for something to eat or drink at any time on 777; no great interest in chatting with strangers to pass the time.
If you have time in DXB go to the lounge and if you depart from A you can descend from the lounge to the plane by-passing the gate.