The 1-4 & 4-1 profiles are steeped in foundation. For these personalities to function they require a foundational basis which they can rely on as they extend themselves outward to others. The difference in these two lines is the the orientation. The 1st line is oriented toward an inward foundation of information, while the 4th line is oriented toward the outward foundation of key aspects of life.
The 1st line is also known as the investigator. The investigator is driven to know detail. This is why a 1st line person often asks a lot of questions. Though investigating and asking questions the 1st line builds up a platform for which they can base their actions on. Most 1st lines who are going to work with people, whether one on one or as a teacher of many, will take multiple classes or workshops until they feel the foundation is complete. Part of this is to feel comfortable. They will often not reach their comfort level until their investigation has unearthed a deep amount of detail.
The 4th line is also known as the opportunist. The opportunity lies within the foundation of the 4th line persons network. It is through their network, that 4th lines will most often find a job, meet their significant other, find their house or their place to live. The foundation of the 4th line is their friends, their co-workers, their home, their family, their job and the groups they are a part of. Because of this 4th lines will often look to have a replacement lined up before moving on. When they do move on from friends, job or location, they will likely hold fast to at least one of these other foundational pieces. For example. if they are moving to a new city, they will probably hold tight to old friends or family until they are settled in the new city and have begun to build a new group of friends.
So what is the difference between these two profiles? The difference is that the 1-4 will be more inwardly or self focused and a bit more driven to get details and or experience. The 4-1 will be more outwardly focused on interpersonal interaction with the investigation coming as second nature. The 4-1 would typically let the 1-4 ask the questions so they can benefit from the detailed information in the answer.