It's only deeper because of that long neck, which has no actual livable space in it.
Funny, I thought there was lots of extra space in the neck and I'm one of those 947' guys.
Come to think of it... I really wasn't having any of the space issues most everyone said there should be, and I still have lots of open space to fill.
Imo, the neck should comprise mostly of support structure and power/lifesupport/comp lines. With a few lounges to explain all the windows. I wouldn't put living quarters in the neck. Even if you did, how many would even fit?
There isn't really a volume problem with the ENT, the only real problem is with the shape. If you mostly ignore the supposed hangar size, and don't mind shinking the cieling height from the 10 ft height of the original set down to 7 or 8 ft to fit in the saucer rim, 947 isn't too bad. Though i prefer the 1080 foot size. Only slightly bigger, and an 11 deck saucer actually makes sense then.