Performance based codes such as the HUD Code allow for more innovation. The HUD Code tells us how much of a load is on a structure and it is up to us to design the home to meet this loading. For example, the HUD Code will tell us how much of a roof load is on a header. We then design a header that will support the given roof load. The design then has to be approved by a HUD approved independent third party engineering firm. After the third party engineering firm approves the design, a copy gets sent to HUD for review. It is only after the design is approved by the third party before we can utilize the design in our construction.

Prescriptive based codes such as the International Residential Code has tables that tell us how to construct the home. For example, if we need to put a header over a window opening we go to a table in the IRC and the table will tell us how to build the header. 

Both types of codes are very effective. The biggest difference is that the HUD Code allows for more innovative methods to be used to construct the home.