Another point in favor of a huge Enterprise: in the underwater Nibiru scene, you can clearly make out the windows on the secondary hull and they're as tall as both Kirk and McCoy are when they enter the airlock.
We also get a scene set on some walkways under the senor dome on top of the saucer (former bridge dome in the Prime timeline design) and the enclosed space is easily twice the size of the TOS bridge, if not larger.
There's a good comparison between the Vengeance's saucer and the Trans America building in San Fran during the crash sequence. That should provide a solid reference point for scale once someone can get a screencap of it. (Spoiler: the Vengeance towers over it.)