Are all of JL's planes converted to solo F seats? The last time I checked (about a year ago) over half the fleet still had the old F seats -- which are 10 years out of date now. Luckily LHR-NRT is a priority route and generally got new F even when JL only operated 6 flights with it. But NRT-Australia will be getting a worse seat. So you might be getting the better seat for only half your trip. Otherwise JL has cut back on catering cost a lot, so the food/drink quality is way down from 3 years ago. But so has BA. Fwiw, BA is planning to roll out a new, greatly improved F (in the works for the past 5 years) which might be on your route by your travel date. So you are comparing new F on JL to "old F" on BA (but might get new F on BA and old F on JL). I'm pretty sure the final pecking order will be new BA F > new JL F > old BA F > old JL F, and BA is much faster than JL at rolling out product (JL was doing 1 plane per year for new F at one point! absurd).

I do agree that the new A380 products are changing the benchmark considerably, and some airlines are updating some parts of their fleet accordingly (77Ws on SQ and CX, 744s on CX) while others are not (yet).