I wouldn't worry about where B4 fits in to the 'scale' of Hertz's definitions of car sizes. I was in ATL last week and got a Hyundai Tucson which was listed as B4 on my receipt. There were also a lot of Nissan Rogues, Jeep Compass, and Dodge Journeys. Also remember that depending on your status you'll have access to the ultimate choice sections at ATL which could have anything that Hertz offers; I've had everything from a Chevy Cruze to a Range Rover Evoque.