I had a 2002 GC and it was unibody, but also had solid axle in front and was just as capable, maybe more so, in stock form as my 2008 S model X. It was a great vehicle to drive. Unfortunately it was falling apart around itself by 180K miles. My X, driven and maintained the same way, is at 330K miles and still in much better shape than the GC when I sold it. I do miss the GC v8 however.
Yes, the new GC's are glorified mini vans like everything else for sale these days.
The wheel base of the 2005 to 2010 JGC was I believe just as short if not shorter than the Xterra with great approach and departure geometry right from the factory. The traction control system was pretty impressive from my experience, too. With some wheel spacers, 275/70/16 M/T's and 2.5 inch lift - even the base model 3.7 Laredo was pretty capable off road.
With all the above I'm still positive the Xterra with the same lift would vastly outperform it. I do think GC's get a rap sheet of being weak or soccer mom haulers though since that's what they were marketed for. Since their price is starting to drop you're starting to see them get heavily modified. I was one of the first doing that back in '07/'08...pretty far ahead of the curve.
Don't get me wrong. The Xterra is a step up; several really. I mean I even have Navigation, bluetooth, xm radio, locking rear diff. and a back up camera...come on now! Much of what it lacks in one area versus my JGC, it outperforms in many others. It's really rather lopsided overall towards the Xterra.
I think the only feature the Xterra lacks that I wish it had was a 6 way adjustable seat. I can overlook everything else. I'm 6'1 and love sitting high up with the seat all the way back with my seat reclined pretty far back when commuting, long legs. I guess I became pretty accustomed to that particular position having been there for 12 years haha.