Its The passenger Size "Stupid"

The long discussed topic about airline seats has missed the over-arching point. It’s the passenger size stupid. Going to the demographic chart will quickly make the point. It also makes the point for purchasing which airplane makes the best sense. The average Canadian woman: Example 

1.                 153 pounds

2.    Canada: The average Canadian woman's weight is 153 pounds (69.4 kg) and height is 5' 3.4" (161 cm). Her male counterpart weighs 182 pounds (82.7 kg), and is 5' 8.5" (174 cm) tall.Dec 4, 2006.

USA Today: USA Women					USA Men
	Data	Weight		Height			Weight		Height
	1988 - 1994	152 lb	69 kg	5' 3.7"	162 cm		180	82	5' 9.1"	176 cm
	1999 - 2000	163 lb	74 kg	5' 3.8"	163 cm		190	86	5' 9.3"	176 cm
	Canadian Women						Canadian Men
	Data	Weight		Height			Weight		Height
	2005	153 lb	69 kg	5' 3.4"	161 cm		182	83	5' 8.5"	174 cm

Wiki

By region

Region	Adult population (millions)	Average weight
Asia	2,815	57.7 kg (127.2 lb)
Europe	606	70.8 kg (156.1 lb)
Latin America and the Caribbean	386	67.9 kg (149.7 lb)
North America	263	80.7 kg (177.9 lb)

The XWB body A-350-9 looses it talking point by the time it lands in Japan. The best option becomes the 787-9 for all operations in the Orient. The human weight and dimension factors are considered for each market. Then comes the configuration metric for the airplane. The majority of the world is not North America. Boeing has long designed its 787 towards the majority in spite of the of the Airbus XWB moniker. Efficiency blended with passenger amenity is what Boeing sought for its original design. Airbus may have opted going five inches wider more for its own manufacturing convenience than passenger sentiment.