The two major differences are the space and size of the units. The TAG is the lightest unit we manufacture with the dry weight starting just over 1,000 lbs. The TAG is mainly a sleeper unit with enough interior space to sit up as well as a kitchen located on the outside rear of the camper. The TAB is a larger unit that has interior space to stand up in and allows space for a full wet bath as well as the option to have a kitchen located inside or on the outside rear of the camper. The TAB is also equipped with a dinette area that will  convert into a queen size bed.