The Insurance Institute for Highway Safety (IIHS) tested 72 popular booster seat models.
"A 5-point harness is an undeniably safer option than a booster seat that uses a lap and shoulder belt restraint. While some parents - let alone kids - do not like the idea of a five or six-year-old still using a so-called baby seat, a 5-point harness is absolutely the safest way to transport a child that is 80lbs. or less in an automobile." http://elitecarseats.com/category/car-seats/5-point-harness-booster-seats/