If the equipment is out in the open, than a cabinet is more secure.
However, if the equipment is located in a locked cage, a rack is much better for cooling. Cabinets need a lot of ventilation and special care for cooling as the heat build-up inside a closed cabinet is much worse then an open-air rack.
Also, with multiple racks, it is much easier to route cabling between equipment. With cabinets, the solid walls between even adjacent cabinets makes routing cabling much harder.
Originally posted by BitOMagic
I would have to say with Karl. A typical rack is 42U. I personally would prefer Cabinets over racks.