If it's happening very shortly and you have a OW/QF status and book the QF 30/29 LHR-MEL/MEL-LHR (as opposed to the one that leaves late at night from LHR), I believe you have a chance of sitting in J instead of PE by booking a PE ticket, because there is no F at the moment (if you happen to be seated in J on PE ticket, you will still get the PE service, not the J service). This is only applicable while F for LHR-MEL-LHR is suspended. I can't remember the dates but I think this was discussed fairly extensively in QF forum. This makes QF more attractive than BA for sure.

However, if above is not applicable to you and if you can get on a BA flight with high J 747 (I think) that has a standalone 28B (and the one on the opposite aisle, I can't remember the seat number), then I would rate BA WT+ higher than QF PE.

That's my opinion anyway. I don't rate QF PE much higher than the BA WT+, mainly because I happen to dislike the QF hardware and the worst airline meal I've ever had (yes far worse than "the ET cheese sandwich" - it was inedible and I rarely call something inedible - it tasted like someone's poured a bucket of salt onto it, and cooked everything until nothing was recognisable) was in QF PE. It doesn't mean you will dislike the QF PE hardware though - it simply does not suit my body shape and it digs into various bits of my anatomy, whereas BA WT+ seat does not.