Smart manufacturing requires digital product data to be shared and exchanged among numerous engineering applications and information systems. But no single product data standard can satisfy every integration scenario. Customizable standardization frameworks for Product Lifecycle Management (PLM) attempt to address this problem by allowing users to add new information structures to an existing data model in a controlled manner. A PLM information model may be either flat or hierarchical. We discuss two approaches. One is based on ISO 10303-239 as an exemplar for customizing flat models. The other is based on Open Application Group Integration Specification (OAGIS) as an exemplar for customizing hierarchical models. We evaluate the two approaches and observe that the type of model strongly influences how well the PLM standardization framework meets each evaluation criterion, and that the best choice is use-case dependent.