IMHO both the aircraft and the seat (at least in J) are better on the A350. The A350 has significantly lower cabin pressure and higher air humidity compared to the 777. As a result, I tend to arrive feeling much more rested.

I find the current iteration of the Cirrus J seats on the A350 far better too, especially with the increased legroom, both in the cubicle in front and on the side. On the 77K/77A, only the bulkhead seats have a wider footrest, and even there, there’s no additional space on the sides.

In Y, the 3-3-3 configuration on the A350 is far superior to the 3-4-3 layout on the 77K.