There's a trip report from my experience earlier this year (DFW-HKG) on the AA 777-300ER. In my limited experience, I would say it has pros and cons compared to BA F. To me the main pros were:

• More table space (enough to dine and have your laptop open at once)
• Two different seating orientations
• More power ports (two power, two USB)
• Reasonably decent wifi
• Cabin temperature was cold (not just not hot, but genuinely chilly)

The food was ok, but really not that different than AA's business class food (they are planning to improve that, but I don't know if they have yet). The seat to me was less comfortable. The seat felt like it was designed by committee, with the touchscreen being a bit odd. Meal and starter choices definitely gave preference to AA Executive Platinum over me.

They had a pretty decent equivalent of club kitchen in the front galley area.

I was in the row 1 window seat, which I thought was a great place to be. While it's right behind the toilet, the door for the toilet is from the front of the galley rather than the side, so it's out of the way.

Overall the experience was fine. Variety every once in a while is nice, and there are a few things that are better than BA. That said, I wouldn't rate it as better than BA, and after 13 hours I was beyond ready to be off the plane, but I had a few more hours to go!