Consider these images, both from A330 economy cabins. The first from Air Asia X, the second from Jetstar -
Air Asia X - A330, 3x3x3 seating (Photos: Airbus A330-343E Aircraft Pictures | Airliners.net)
Jetstar - A330, 2x4x2 seating
And with the 2+4+2 config, 100% of seats are within one seat of an aisle. With the 3+3+3 config, 22% of seats are two seats away from an aisle.AAX/D7 - 3+3+3 = 9 seats + 2 aisles
JQ - 2+4+2 = 8 seats + 2 aisles
simple reason the seats look thinner
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With 3+3+3 the best you can hope for is three seats to sleep on. With 2+4+2 there's the possibility of stretching out on 4 seats -- Better than J .And with the 2+4+2 config, 100% of seats are within one seat of an aisle. With the 3+3+3 config, 22% of seats are two seats away from an aisle.