The cabin's humidity, simulated altitude, and oxygen density is much higher on the 787 and A350 because these planes are carbon fiber skinned. The stronger skin allows the cabin to be pressurized at a lower altitude equivalent. Overall, the 787 and A350 have a cabin altitude simulating 6000 feet or less (max 6000 feet, usually much less on average). On other metal bodied airliner planes, the cabin altitude is simulated at 8000 feet or less. While that isn't a significant difference, remember, Denver is where the athletes go to train. Denver is about 5000 feet elevation. Santa Fe, New Mexico is about 7000 feet! But I don't see as many athletes going to Santa Fe!