You need to import each person individually so you can check the quality of the information for each person, otherwise you will end up with a garbage tree like many that are online today.
It is not hard to do a couple of checks in the many online database to verify each person or family. When you check a person consider the physical limitations, like travel, condition of the person and family. (a family of limited means is not making round trips to Europe every two years in 1800.)
There is another test that many owners of online trees fail to perform. Is the person of consideration where he is suppose to be location wise and chronologically. If the family lived in Reading all of their lives They don't suddenly appear in California for a brief period in 1850. A person can not be in two places at the same time, and a person can not die in 1850 and be in the census in 1860. or living in New York and Pennsylvania at the same time in 1820.