Most manufacturers use the same components, so you won't see a lot of difference. The difference in fit and finish is the main 'tell.' But in a used unit, as you are interested in, previous owner care and maintenance is much more important. Ask for maintenance/service records. If you use the chassis VIN number, Engine and transmission numbers, you can contact the manufacturer and find out if recalls or issues have been dealt with.
Check the roof and all caulked joints, looking for upkeep and maintenance of those areas. Hire a professional inspector, you're spending as much as a house costs, why not have an expert's help?