Most people don't realize that the strength of your installation is significantly impacted by the type of fasteners that you choose for your project.
When you secure the sign with the set screw method and the wind blows in either direction of your sign then only one wall of the sign bracket is actually supporting the wind load. The main benefit of using this method is that you can save time and cost from drilling holes in your sign and set screws can be much more economical.
When you secure the sign with the bolt-thru method then both walls of the sign bracket are supporting the wind load; therefore increasing the overall strength of the installation so it can take larger wind loads. An added benefit is also if the bolts loosen then the sign isn't in any immediate danger of falling as the bolts are still engaged through a hole in the sign.