After having done a reasonable number of these trips with both carriers, my two bobs' worth is;

1) QF is much better for food and wine. One of QF's strong points.

2) QF offers champagne as a welcome drink, but BA doesn't.

3) Toss a coin for service. It's variable on both carriers depending on the crew.

4) The QF cabins have been refurbished, including the toilets, since skybeds were introduced. So they are nice and fresh whereas I now find BA cabins a bit tired and worn.

5) I like QF 32, even from LHR. I'm not a good sleeper on flights, so I find night flying boring. The day trip down from SIN to SYD is one of my favourites, even after having started from LHR. A couple of drinks, a bit of a doze and then to bed at the other end.

6) The more I fly the skybed the more I like it. I'm only 5'7" so I can strech out on both, even without sliding down on the skybed. I find the BA cabin layout cluttered, especially on the main deck with the 2x4x2 configuration and the reverse facing seats. BA also has 70 seats in NCW, meaning more punters than QF's max 50.

7) I have had WP status since early 2002 and have only had one op-up in many flights on both carriers. That was recently on QF 32, J to F.

So it would be QF for me, but BA would still be an enjoyable flight.