Well, I just made a similar decision to yours, but for me it was 83" A90J vs 77" A80J. I also sit 12' back, and my room is similar to yours - kind of bright during the day, and always some lights from the open floor plan on at night.
From all my reading of hundreds of pages of posts on both owner's threads, the main difference comes down to the A90J being brighter in HDR (specular) highlights. That probably also results in being able to sustain a brighter SDR image when pushing brightness to non-reference levels.
I am coming from a 2009 plasma, so either of these TVs are way brighter than my plasma. To me, the A80J was the better value for our situation, giving me a much bigger screen than the 65" without having to pay 83" money. For you it would boil down to screen-size vs brighter HDR highlights instead of being more of a $$$ decision.
I am also not a 100% stickler for accuracy - I don't watch in a dark room, I'm happy to watch SDR at brighter than 100 nits, director's intent never trumps my personal preference, and if my HDR highlights don't quite reach the brightness level of the director's intent, I don't really care.
All that said, I personally find the A80J spectacular, especially at night or with the blackout blinds pulled so it is not competing with sunlight. And the big increase in size makes a big difference in enjoyment of movies. I couldn't be happier with this TV, and if at some point down the road I'm not, then hopefully by that time, the big A90J will have dropped in price enough to change my value equation.
p.s. - I don't game at all, so that played no part in my decision.
From all my reading of hundreds of pages of posts on both owner's threads, the main difference comes down to the A90J being brighter in HDR (specular) highlights. That probably also results in being able to sustain a brighter SDR image when pushing brightness to non-reference levels.
I am coming from a 2009 plasma, so either of these TVs are way brighter than my plasma. To me, the A80J was the better value for our situation, giving me a much bigger screen than the 65" without having to pay 83" money. For you it would boil down to screen-size vs brighter HDR highlights instead of being more of a $$$ decision.
I am also not a 100% stickler for accuracy - I don't watch in a dark room, I'm happy to watch SDR at brighter than 100 nits, director's intent never trumps my personal preference, and if my HDR highlights don't quite reach the brightness level of the director's intent, I don't really care.
All that said, I personally find the A80J spectacular, especially at night or with the blackout blinds pulled so it is not competing with sunlight. And the big increase in size makes a big difference in enjoyment of movies. I couldn't be happier with this TV, and if at some point down the road I'm not, then hopefully by that time, the big A90J will have dropped in price enough to change my value equation.
p.s. - I don't game at all, so that played no part in my decision.