About Quantum dots from QD Vision in X900A, W900A
"Color IQ™ " is an advanced light emitting semiconductor technology developed by QD Vision, Inc.
By integrating QD Vision's "Color IQ" optical component with Sony's unique display technologies, this television set achieves a significantly wider color gamut, which provides a far more natural and vivid viewing experience."
Even when both have QD but W900A and X900A look different because they use different panels or have different coatings
W900A (someone in W900A thread mentioned it is a 12 bit panel, confirmed by their sony insider?)
Deep black panel
"Choose a BRAVIA TV with a Deep Black Panel and you'll notice the difference in your whole viewing experience. The panel has a low-reflective, clear surface which helps deliver high contrast, realistic detail and accurate colours. Keep your eye on the action with no distractions and no ‘wash-out’ effect on the picture when light from lamps or the sun hits the screen."
X900A, X900B (OptiContrast Panels)
"OptiContrast Panels have a special resin layer which absorbs any diffused light delivered from the backlight. What you see is high contrast and natural colours on screen - bringing out detail in the darkest movie scenes - and a real sense of depth.
This special resin layer inside OptiContrast Panels also absorbs ambient light in the room. When watching TV, it reduces glare from light sources such as lamps or sunlight."
Flagship models: X950B, X940C have both Deep Black Panel and OptiContrast Panels listed in their specs
Unfortunately people who bought X850B or W850A, W950B series don't have either of them. X850A has deep black panel.
In my opinion, Sony left out QD in 2014 to make more profit and they were confident that they could do it on their own. I remember W900A was like $3000 when they started, still very highly praised on Amazon and here. They stripped down and made W950B which sucked in 2014.
In 2015, I really hope they bring out something good with the X1, flashship X940C is a X950B based on specs, the only model you can get all the goodies (X1 pro, deep black, opticontrast, FALD).