Generally speaking the seat is the most significant difference between cabins, most certainly between Y and J.
That being said, on a daytime flight service becomes more important to me, where I'm not trying to sleep but want to rather enjoy the service, food, drinks, the ceremony of it all. While seat should still be comfortable it's less important.
Originally Posted by
Swanhunter
The seat - and most specifically the bed. This is why BA was a world leader 15 years ago, and not so much now.
Nice username