Size of the Enterprise = the height of Spock. Or McCoy's shoe size or Uhura's bra size. It's a TV show and for the modern one they've replaced the ship with a new young "actor". When you're watching TOS, it's 289m with the Franz Joseph floor plans or whatever and if you're watching the modern one it's 442m and Pike's bed has had a major upgrade compared to the one he was laying on chatting to Boyce.
I know we're ultra-hardcore fans, but it's a television show. SNW and TOS really fit together about as well as Smallville and the old Superman movies but we are supposed to suspend our disbelief and go with the new modern look and modernized characters and stories that work in isolation but make a mess if you try to see it as one big whole.
And for what it's worth, the 442m size of the SNW Enterprise is totally broken by the shuttlebay, just like TOS and the Kelvin movies. But the windows, sets and stuff were all made for the 442m size and that's the size they say so that is the size it officially is.
And this from the guy who went insane between 2009-2013 obsessing over this stuff. And while fun, you'll never ever actually fix it by pulling a number out your bums or making the old version the size of the new one.