Cathi, many of your questions have been answered before in various threads.
But to recap, yes the Oliver is far superior as to winter service.
The double hull offer a lot of advantages:
Insulation is applied to the underside of each hull. So you have 2 layers, plus a dead air gap in between.
The dual pane windows
are true dual pane and glass, not acrylic.
All the plumbing and tanks are between the hulls, as is the furnace
and the water heater. These effectively heat the space where these items reside.
Besides offering thermal protection for winter weather, or summer weather for that matter (an Oliver should be much easier to cool as well), the double hull provides a VERY strong structure. All the cabinets and bulkheads are molded into that inner hull. That makes their load capacity very high, as well as no need for any penetrations to bolt in cabinets or walls.
An additional benefit of the double hull should be sound insulation. A trailer with this setup should be fairly quiet inside.