I thought the Liberty was in a different size/weight class than the Xterra?? I always assumed the Liberty would be more competing with a Ford Escape, whereas the Xterra was more towards the Ford Explorer (old style, not the newer [more] bloated Explorer)??

Maybe not, but I don't think the Liberty is anywhere near the Xterra's class. It's just a touch too small for that. And besides, it's only got a 3500 lb towing capacity, and a very weak 6 cyl. engine.