The 787-900 is easily the quietest and best plane I've ever been on. Far and away.
I have not been on the A-350 yet, but in comparison to the A-330 or A-380, or the 777/747/737, the Dreamliner is like a library.
The only negative about the Dreamliner is that the vast majority of airlines have chosen the brutal 10 across in coach, when it was designed for 9.
A-380 Emirates was probably the most disappointing plane I've flown relative to expectations. Not enough bathrooms, takes forever to load/unload passengers, food was equivalent of domestic food. It did ride like an old smooth Caddy though, that's one thing I'll say for it, smoothest ride out there.