I agree, MEL-SYD or SYD-BNE being only 1 hour flying time not a huge difference, but being based in BNE, where BNE-MEL, BNE-ADL, BNE-TSV, BNE-CNS are all 2 hour flights I do regularly, there is a BIG difference being able to get a seat in row 4 on a 738 (exit row leg room with out the exit row).
Seconded. I don't really care too much with the hour or less flights eg SYD-MEL-SYD, SYD-BNE-SYD, SYD-CBR-SYD (er well actually the CBR run I do like to be at the front as the taxi's are a nightmare out of CBR) and I will normally get an aisle in the first 3 rows.
Anything longer than that, especially SYD-PER-SYD I'll really try and get the seat I favour.