Which aspect ratio is better for 3D movies? Fullscreen, widescreen, variable etc

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i personally would only shoot in 16:9...also i don't know if other people have seen the same but my local 16 screens+ theater changed every screen to default in 16:9 and when they show a 2:35 or 2:39 movie it just doesn't take up the whole space. it used to make more sense when they opened the screen left and right for those movies but that doesn't seem to be the case anymore.