The difference between the stealth and the NG is one inch in width. I just bought the NG and it is by far the best bag I've ever owned. Quality constuction, GREAT handle, smooth, smooth wheels....the only drawback(if you want to call it one) it's a little heavy....but hey, you know this bag will last.
The reason they still make the stealth is that it will fit under the seat in the 737's cockpit.
BTW, if you order one, get the handle wrap(it's five bucks) so the foam handle won't wear out. worth it.
hope this helps,
the turtle