I flew AA F LHR-LAX (a daytime flight) recently and the experience stood up quite well against QF F on the A380 (though that was a midnight departure, much of which I spent horizontal).
The AA seat arrangement is quite similar in layout and size to the QF (A380) one, though the screen is somewhat smaller and the controls (as you would expect) not quite as modern and sophisticated. I saw no evidence of a mattress etc. (though it
was a daytime flight). The seat was comfortable.
The main meal was good enough (though I paid the price for not checking the pre-landing snack well enough - it was 'turkey sandwich' vs. 'pizza' and whatever came with the turkey sandwich was definitely not to my liking). Once they had worked out I liked red wine

oops

the supply did not stop (offered, not requested, apart from the first one) until I said, a long way into the flight, 'Enough thanks!" (it was a Chilean wine - pretty nice). The FAs were certainly 'experienced' and friendly enough without being 'familiar'.
Movie selection was good (I watched the entire Lord Of The Rings trilogy from their 'classics' menu

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and the Bose NC headphones were the best of all the airlines on that trip. I did manage to get horizontal for a short time and found the bed comfy enough.
Flagship Lounge at LHR was adequate but nothing to write home about - no better IMHO than a typical QP (in fact a decent QP is probably better).
Haven't flown JL F, though a J flight NRT-SIN stood up ok against other carriers' J.
In summary, I was pleasantly surpised though to be fair I have very limited international F experience to be able to compare.