For carrying 4 bikes I'd say go with the
Yakima Doubledown 4 bike hitch rack. This is an awesome fold down hitch bike rack and you can't beat the price. Carries up to 4 bikes and delivers excellent stability. The included Yakima SwitchBlade cradles also ensure the bikes won't swing into each other or the back of your cars. The optional
Yakima DeadLock security system will simultaneously lock the hitch rack to the car and the the bikes to rack itself. The best part is the Yakima DoubleDown hitch bike rack will also work on both 2" and 1.25" hitches right out of the box, no adapters needed.
Also, FYI this hitch bike rack is also available to carry 5 bikes
Yakima Doubledown 5 bike hitch rack
and a slimmed down version for just carrying 2 bicycles
Yakima Doubledown 2 bike hitch rack