For your booth at a trade show, the greatest long distance visibility that you can create is with a hanging sign. So by all means, if you are allowed (usually you must have a island space) consider such a sign. However, when you go out to design the sign, consider these key life cycle cost affecting variables:
Freight handling, also called drayage, costs are usually the second highest costs of exhibiting at a trade show, second in stature only to the cost of exhibitor rental space. Packing and shipping your display materials to reduce these costs is critical. Freight Handling Penalties of up to 50% of total freight handling fees are awarded for packing methods that do not conform to show guidelines as specified by the general contractor and late shipments.