For sunset viewing you really are between a rock and a hard place.
As posted, on the 7th the Sun is due to set in MEL at 8:32pm
From 11km high you may be better off on the 8:30pm flight where from the A seat you'll chase the after glow and final sunset - on the 7pm flight it will still be too high in the sky for sunset even upon landing.
Note that during the latter third of the flight, the aircraft will be heading more into the sun than laterally. Normal routing is over Wollongong and across to areas around Yarra Glen before a Westerly course to MEL.
http://www.gcmap.com/mapui?P=SYD-wol...2b%22%25U%2212