I'm not convinced about "lower cabin altitude" marketing for the 787. Based on checking my altitude watch on a 744 flight and a 787 flight the day earlier - both about 8 hrs duration, there was almost no difference in the final cabin altitude an hour before descending. Both about 1850 m. Same with the 777. Of course, the 737 consistently has a higher altitude at the end of the flight ( about 2200 m or more). So if Boeing are comparing the 737 and 787, then yes, there is a big difference, but not against their twin aisle heavies.
Yes the higher cabin pressure and humidity levels on the 787 (and later the A350) are just urban legends, albeit ones that have great legs.
https://www.flightglobal.com/news/ar...le-cab-369425/
Several key points in the linked article include:
1. The existing modern Airbus widebodies already keep cabin pressures below 7,000′ except when reaching FL 400.
2. Humidity is actually better in Y than in premium cabins because of the density of pax.
3. The only real improvement in the 787 is that the air circulation system brings the humidity in premium cabins up closer to Y standards. It does *not* have any active humidifiers (except for the cockpit).
4. There frankly isn’t a ton of evidence that pressure and humidity really make a difference for comfort anyway.
5. Humidifiers can be installed in metal fuselage aircraft too; the corrosion argument is a bit of a red herring.
6. The main obstacle to installing humidifiers in any aircraft – metal or composite – is that they require water…which of course weighs a lot.
7. Given the last point, I confidently predict airlines will start installing humidifiers just as soon as they begin converting their 787 and 777 Y cabins back to 8 and 9 across respectively.
My apologies in advance to any B787/A350 flyers who were benefiting from placebo effects.