The bigger Lance trailers don't have a flat roof. The Lance is much lighter, allowing you the ability to tow their largest trailer with a half ton. Lance touts their huck-bolted frame. I'm not sold on the concept.
Arctic Fox's are heavy, and solid. As already mentioned, a much better option for off road use.
You may want to also check out Outdoors RV trailers. They are a spin off from the Arctic Fox owner, and are very similar in build quality, but have some different interior decor, which might appeal to the wife.
If I had 3/4 ton or larger truck, I'd opt for the heavier brand. But since I do have a half ton, I'm very fond of the Lance line up.