I didn't expect that the cabin environment on the newer generation 787s and A350s would make much, if any, difference, but the first time I flew on a 787, I did find it to be a better experience, and less fatiguing afterwards. Same with the A350. Every plane is loud, and I never fly without some ear protection, but they are smoother. It's akin to getting into a nice, modern car, and then getting into your old jalopy and realizing that refinements have been made in the state of the art.
When they are an option during booking, I'll look for the newer planes. Or the 777X whenever it actually enters service.
Only issue I've had during the past few flights is with the temperature. Whomever had the climate controls on a couple of the flights kept the cabin very cool, but that's isolated to the flights and not the nature of the plane.
Another minor thing is with the electro-dimming windows. The cabin crew can override the controls, and taking a peek outside isn't possible, even during non-sleep/daytime if they deem that they should all be dim.