I've worked with Ritz-Craft homes and been to the plant and most of the companies in PA. There are a few plants that put out a product that as a builder you are happy to turn over the keys to the house because you know the quality. Modular construction is like anything else in this world where you have choices. There is the good, better and best.
This industry has not done itself a favor in promoting itself and people do not know what a system engineered home can be. This is the only way to build today. The building trade contracted since the economic decline and some people in the field are hard to find if they are any good, so some of the people working today may not be trained well.
In the factory you will have a number on inspections as the house moves along, on the site, you get a few and if the builder knows the inspector, maybe none. Take the tour if your close to the plant, you'll be surprised at the quality.
Think about this, would you want your car built in the driveway or at the plant with people who do this everyday?