I would think that a couple of the reasons that NW touts off road use is their frame and suspension. If you look at the gussets they weld in and along with having shocks it should be better than most all of what comes out of Indiana. JMHO here though and take it for what you want but I think their use of 'Off Road Capable' is a little overblown. It really appeals to PNW buyers where they camp in more rustic environments. Selling a TT with off road capabilities to someone in Nebraska would be silly. It's sorta like buying a Ford F150 Raptor and never going off road.
That being said they're built a little stronger than the competition so even on pavement they should hold up really good.
I've had no issues with my NW Fox Mtn as far as structure goes. And there's plenty of other brands that have held up well on pavement too.