I'm going with the 366 meter length until absolute concrete evidence is presented otherwise and no the Blu-Ray picture will not suffice it was just an inflated image of the ship. Random quotes from various ILM staffers won't work either. A technical manual designed by the people who finalized the ship's design will do nicely but we know the likelihood of that coming to fruition. Their own movie contradicts what they say anyway.
Yeah mate you go bury your head in the sand it will make you feel better, when you pull your head back out the NuEnterprise will still be as big as the Enterprise D (definitely longer) and the Vengeance will still be as big as a Romulan Warbird.