AA 777-300 J is just fine unless you can guarantee you'll get a new BA club world seat. I'm not sure if they are dedicating those to the JFK-LHR routes or you could still get a swap and be relegated to the older, cramped CW seating.

As mentioned, don't waste an SWU on going to F on the 77W. You may even find upgrade offers that make it more worthwhile. But even so, the 77W J seats are quite nice.